You will NOT have to dismantle the driver's door to get to the lock/unlock wires. All the wires are located around the driver's foot/kick panel area. Main ones like 12V, accessory, and ignition are located inside the steering column. Solder is always the best, but not necessary. As long as you can strip a small piece of the sleeve off, wire tie it, and secure it with electrical tape, you are fine.
Adding an alarm will NOT void your warranty. Search for the Magnuson-Moss act, and use that for the dealer if they ever give you any troubles.
I'd tell ya to come up to our store to have it installed, but it's probably too far of a drive.