rear door won't open
 

just bought a used 2002 Sierra 2500 HD extended cab. i think this truck is great even with 160k on it. It seems to be built like a tank.
i've repaired some things on it with help from reading this forum like heater blower resistor bank, new PS exterior mirror, replacement horns, cabin air filters and other small stuff.
i do have a couple of questions i didn't find in searching the threads.
1 the rear passenger side door won't open. the latches for release from outside on both left and right doors don't work (they just flop around) but i can get the left door open using the inside release. the right seems to release at the top but not the bottom. i can't get the inside panel off with the door closed.
any advice?
2 tires are E rated. what pressure should i run with the truck empty for a little smoother ride(driver only)?
3 inside rear view mirror seems to be dimmed all the time. is there a light sensor somewhere? temp and direction work ok.
thanks
mac