I haven't finalized on an amp yet, but I'm leaning heavily towards the Alpine PDX-5. That'll drive four speakers and a sub just fine without going too far into 'thump' territory, and it's tiny (and well thermal managed) enough to go under the passenger seat, safe and out of the way.
The door panels couldn't be easier. It's cargo van!
For the driver's and passenger's doors: Use a phillips screwdriver and undo the 9 screws on the sides and the bottom of the door. Very carefully pop off the long plastic 'cap' (the textured part) off the front of the pull handle using a putty knife or other thin-thin blade. Be gentle or you'll marr the plastic up a bit. Inside the now-open handle you'll find two Torx T-20 bolts; remove those. Inside the door-latch you'll see a tiny round circle with a screwdriver blade slot. Use a tiny flatblade to pop the circle out; it's a simple push-cap atop one last torx T-20 screw. Then slide the 'cup' off the door-latch to free it up. Now all you have to do is pull the bottom of the door outward and lift the whole thing up. Note: on the driver's side, if you have the power mirror option you'll have to reach up under and un-clip the cable plug connected to the power mirror controls once the door is free.
For the rear cargo doors: use a putty knife under each of those huge back 'plugs'. They will pop right out; they're just plastic bosses. It will take some pretty serious elbow grease but they'll come out just fine. Then the two far-too-thin-to-be-useful MDF panels will be free and you can get inside the doors. Make new ones with a router or jigsaw out of 1/2" MDF (or thicker), put a little dynamat on the inside against the metal and mount 6x9 speakers. Route the cables through the flexi-hoses that connect the doors to the main body and then along the base rails up to your amp (or radio head unit).
Backup camera: See those two knobs up high on the inside driver's-side rear door? They're wingnuts meant to be undone by hand. Undo those and that odd rectangular 'plug' comes right out of the back. Mount your camera to that plug (or *in* it if you want to be creative) and run the wiring down inside the door. Then remove the lower MDF panel as before and route the wire the same as you did for the rear speaker. The way this little plug is shaped I'm sure someone overseas has a ready-made backup camera that plugs right in there. I can't see any other real use for it!
If you respond to this I may not be able to get back to you for a few days. Tomorrow morning I head out on a 2500mi cross-country trip in the TC. I'm taking Highway 50 (the Lonliest Highway) from California right across the nation to go visit some family. Back in a bit!
--T