Well, I'm not sure how much help I can be, but seeing as no-one else is answering, I'll give it a shot to the best of my knowledge.
One obvious caveat, your ability to source parts will depend on where you live. In the US, that's most likely going to be TCSS for saber specific parts. In Europe, JQ Sabers is a good bet, they stock plenty of TCSS parts and more (email them and ask if they've got what you're looking for, never hurts.) further out, and you're going to have to try and find electronic specialist sites based in your country for parts like batteries, switches, recharge ports, etc.
Hilt: While I'm not a massive fan of Dremels, with the right cutting disks (reinforced fiber) and some patience, you can cut through thin aluminium, brass, and steel. If you don't fancy that, there's still the option of the PVC saber. it's a little outdated now, given the prevalence of MHS parts, but for the sabersmith on a budget, a little PVC plumbing pipe, matching fittings, paint, basic tools (drill, hacksaw/dremel) and imagination can still make a fancy saber. Here's a link to how to build them. it's a little old now (as are most of the tutorials listed on this forum, saddly) the technology has moved on a little, but there's still some valuable info to be taken:
Qui-gon Jinn's (Jay-gon Jinn's) PVC Sabers Sound:. can't say I've used a Pico Crumble before (I'm still a bit of a Padawan, only two builds under my belt) but it's a Plecter Labs product, and there's plenty of manuals at their site:
Articles - Plecter Labs - Props Electronics (READ THE MANUAL) The question I would ask is this: do you have a Pico Crumble already, or do you intend to buy one? the availability of saber sound cards can be... in flux. Plecter Labs only make so many every now and then, and they sell out fast. An alternative is cannibalising a cheap Hasbro toy for its soundcard. you'll need to modify it a little :http://forums.thecustomsabershop.com/showthread.php?7587-Economy-Version-Hasbro-Sound-Tutorial but it's still a workable solution that produces good results
Battery: Okay, so you can still just about use AAA batteries, but it's really not recommended. These days, most sabers use rechargeable Lithium-ion batteries. According to the Pico Crumble User manual (ALWAYS READ THE MANUAL!) the Pico Crumble was designed to work with an 18650 or 14500 li-ion. however, li-ion batteries have their problems (they're bigger than regular batteries, you have to take care storing them and recharging them, and they can still explode, even with protection circuits.) If you're making this saber for a friend, you can't guarantee how well they'll take care of it, or if they're familiar with how to safely handle a li-ion battery, then plain AAs and AAAs might be worth looking into.
The catch there is that you'll need to install additional components into your build to regulate the power of the batteries.
Okay, so as to your questions:
1:Heat shrink. use plenty of heat shrink. and resistors. I don't think you'll need a momentary to latching convertor, as the pico crumble only works with momentary switches. I'm not sure if I'm missing anything obvious, but I might be.
2:While you can fit everything in loosely, it's really not a good idea (the accelerometers on the sound card won't be as responsive, wires could short/break from rattling around, etc) a chassis or a sled is a good idea, but requires a bit of planning as to how everything will fit together. I can't find a tutorial, so you'll have to employ a bit of google-fu to find out how to build them
3:Yeah, all soundboards also control the LEDs (seriously, READ THE MANUALS). they're marvels of technology for the tiny they are. all hail 'Erv and the Powers of Buttered Toast.
4: As I said earlier, rechargeable are pretty much the norm. ALWAYS GET PROTECTED LI-ION CELLS! Now, the catch here is that given how Li-ion can be dangerous, it can be nigh on impossible to get them shipped abroad. If you're in the USA, TCSS can ship them to you (and I think they can ship to Canada) but they won't ship them outside the US, so you'll have to find a local supplier. recharge ports are easier. the standard is a SwitchCraft 2.1mm DC port
http://www.switchcraft.com/Category.aspx?Parent=19 Those are the ones that TCSS sell, but you can get them easily from online suppliers or electronics shops. wiring diagrams you'll have to google for yourself, but there are plenty of tutorials and videos online.
be aware that if you do go for rechargeable batteries, you'll also need a charger to go with.
5:Well, that's one question I can't really help with. far too many variables at play.
the biggest catch is probably going to be the soundcard. If you have one already, hurrah! if not, then it depends where you intend to get one from. TCSS have them in stock right now, so if you can go directly to them, awesome, do that. if you can't (say, like me, you live outside the USA) then your best bet is going to be to buy them directly from Plecter Labs. But, as 'Erv only makes a limited amount available every now and then, you have to like Plecter labs on Facebook, keep an eye out for announcements on stock availability, and pray that you see one there's still stock left, because they sell out FAST.
seriously. I missed out on one around may last year because I took a lie-in on the only morning I didn't have a work shift on and woke up 30 minutes after the announcement went out. by the time I got to my computer, they were sold out. very popular stuff.
This is the one advantage a Hasbro economy soundcard will always have over Plecter labs: you can buy them any time.
after that, the hardest to get will be the battery, assuming you go down the li-ion path. ALWAYS, ALWAYS GET A PROTECTED LI-ION BATTERY! you don't want your saber to go the way of a Samsung Note 7.
as for the rest: you can get most of the electronics on ebay, although it might be hard to find a high power LED in the right colour (plenty of yellow ones for regular lighting, colours, less so) so you'll probably want to seek out an electronics specialist site or a Saber Specialist site for that.
the hilt body itself will be the least of your problems. You'll have plenty of options just dropping into a hardware store and having a run around the plumbing section.
I'll also throw in a couple of links I've found handy in my builds:
Machining without machines A Few Things I?ve Picked Up Along The WayHow To: Brass Caps for Tactile SwitchesNew to saber building? Where to start? List of great tutorials and other info! the tutorials here are a little outdated, but have plenty of valuable information for a beginner.
And that's all I've got. Best of luck with your build!
Anyone got any other ideas?