Running cable through vapor barrier

Since you're going to have the walls open, I would use pre-faced fiberglass batting. The rolls give you more flexibility than the pre-cut batts if you have non-standard height walls and they're usually a little cheaper per square foot, but I see special offers in the big-box stores all the time so shop around.

There's no special trick to installing it, but wear a dust mask that's rated for fiberglass dust. The vapor barrier goes on the warm side. I usually cut pieces to length before installing them in the wall (but I'm an engineer and can't help myself! :), but you can cut it to size while it's in the wall if you're not as OCD as me: put the loose end at the top of the wall, unroll and stuff until you reach the bottom then cut it off. Run a bead of adhesive along the stud, then unfold the flaps at the edge of the insulation on one side of the stud and press into the adhesive. Repeat for the insulation on other side, then staple the two of them into the stud. Tap the staples in with a hammer if they didn't go all the way. Done!

I don't have a book recommendation, but it's easy to learn how to do it.

To help you with the terms, what you're looking at from above is the top plate. Frequently there are two 2x4's for a top plate. Two boards are used for added structure at the joints and extra fire proofing. This gives you about 3" of wood to drill through.

As ChrisF mentions, you should run a stud finder up and down the wall cavity near the halfway point to see if any fire blocking has been installed. This would be a single 2x4, and will almost always be in a wall if the ceilings are over 8' tall.

You'll significantly reduce the odds of insulation in the wall if you are doing this project on interior walls. You should also be avoiding any electrical in the same wall cavity (between the same two studs). You would see an outlet, switch, or wire coming out of the top plate if this were the case.

As for the actual wiring, I've used these low voltage mounting brackets for the hole in the wall. Place the bracket on the wall where you want the opening, mark the corners and sides, and cut out the drywall with a drywall saw. Test fit the bracket and file back any spots that are blocking you until you get a snug fit. Then bend the tabs back into the wall and tighten them with a pair of pliers. On that bracket, I use a modular plate (these comes with more openings if you need them) and then an ethernet jack mounted in the plate. You can also get jacks for cable, phone, stereo, etc.