I can answer a couple of your questions.
Decasing a laptop can range from pretty damn easy to unfrickingly frustrating. I've run the gamut of turning my screen broken Macbook Pro into a headless unit that is now our kitchen PC (ok, technically not headless anymore), to getting stymied by an old Sony Vaio, to just the other day completing the "tick me off" decasing of an Acer. The latter took me a few days before I traced two hidden screws preventing me from my goal, and the internet was no help.
So, all that said: google first, then just go for it, but go slow. If something seems stuck, there's probably a hidden screw(s) somewhere...so take your time.
Now for sound: that too is highly variable. I'm in the middle of a jukebox project that until last week was going to be run by a repurposed dell optiplex (P4 1.7 IIRC) with basic on board sound. Then, a lady gave me her busted Acer 4420 Athalon X2 1.9gHz laptop. She'd gotten pissed at it because of a broken power jack and pretty much flung it across the room, destroying the LCD as well. After getting it decased, de-LCD'd, and hot wiring the power I resurrected it. The onboard sound for this laptop is far superior to the Dell I was going to use, and far more configurable, so it's now the heart of my juke. Not top of the line, no, but pretty darned good for free.
Mine too will be run via an ELO 15", but I'm not going for a hang on the wall style but for a "conversion" of an old (.......) cabinet. I'll be posting about it in the very near future.