I've run wires through the door before
It works OK just make sure they don't get caught in the hinge. Later on you'll be pissed though, I suggest going for running through the firewall.
You can attach to either the battery or the lug where the LARGE wire enters the UNDERHOOD fuse box.
The system in my alero was the first one i'd ever done, and installed in around 2hours... I think it's simple enough for a money to figure out.