For starters, I'm not sure if you need the vapor barrier or not. I'm leaning towards a YES to that but I think it depends on what's between the block and the 'outside world'. If there's a barrier there, I don't see the need for a 2nd one because it would only trap moisture between the two. I'm assuming the wall(s) are all totally and completely ABOVE grade.
You'll need to install Furring Strips to the block wall first before you hang the drywall. You'll need a power nailgun for this. Now, this depends on where you live. If you live in relatively warmer climates, you need only to install Insulation Board between the strips. If you live in the NE like I do, you'll want to build a studded 2 x 4 wall first, then insulate w/R-19 fiberglass insulation.
Since you're in the preliminary stages of this project I have a couple of suggestions. Based on your ?'s, you have a log of upcoming concerns. (Running electrical wires through or over top of block, through perhaps studs, all for starters.) By my saying that you're asking relatively basic, yet important, questions, you want some help. Visit the library and Home Centers and Book Stores and buy / borrow some books that address home renovation. You'd be surprised at how much you DON'T know. You're not alone, and I make this recommendation to a LOT of folks. What I say is: If you're gonna save some $$$ on doing the work yourself, then spend some $$$ on some good books. That's $$$ well spent. RE: The electrical 'item' I mentioned - You don't want to accidentally put a nail into a 120v line while hanging a picture, do ya? Preparation (with the use of this Forum and some good books) could save you a lot of problems down the road. At least this could save your life.
You know where to find us. My best to ya and hope this helps.
Jay J -Moderator
PS: Just be sure whatever books you buy have info on finishing a block wall. The BEST scenario would be one that's being done above grade. You could still use the info about block that's being finished below grade, just understand that the 'water issues' are taken into consideration right directly ...