I have no idea. There's a GM mount kit that Walmart keeps in stock, but the one specifically for 01-03 GP's I think they recommend to special order, but I used the earlier model one, once you find the right bracket, will fit into the '01-'03 mounts
Haha no problem. That headunit looks fine for what you need, just make sure you have a mount kit for it.
If they are like the other Audiopipe amplifiers, then you should be fine at 1 ohm. Most A/B class amplifiers are not meant for 1 ohm applications, or even 2 ohm. I haven't found much on the lower wattage versions, but the upper wattages of the same class have had excellent reviews for the price. Run it at 1 ohm, with your subwoofer running parallel (one coil wired up to the other) and you should be okay. Also, make sure you have money for a wiring kit; for something like that, you should be fine with 8 gauge wiring.