rear door, hatch won't open

I reciently bought a used 96' jeep grand cherokee... I had the transmission rerpaired, and the rear axle bearing and spider replaced. 1)The parking break(inside the disk assembly on rear needs adjusting, which way up or down?)2)How do I get the rear door open?, key doesn't work and electric door lock doesn't work, I have limited access to latch box from inside. this is somewhat important because I need to replace a break light bulb.
key also doesn't open passanger door. Auto door unlock need to be replaced,this I know.

3)The transmission seem to be a little hard shifting to, if its not an easy fix I'll take it back to transmission shop.

4)driver seat is floppy in mount, pins or something else.

and sorry lastly5) Infinty gold sound, not work, I have aftermarket radio, but no sound...

help would be great.

Assuming that the key is the right one try to spray penatraiting oil on the lock. If that dosent work you will have to take off the back pannel, not a easy job with the door closed. You should be able to get it off enough to move the linkage and open the door. On the brake up is to tighten down is to loosen.

Is the rear hatch locked or just stuck, these tend to get stuck mine does this every once in awhile where it will not open this si what I do to get it open, make sure the doors are unlocked (use the power lock/unlock switch to unlock doors) then push in on the door while pulling the handle and lifting the liftgate or try giving the door a couple firm taps with a closed fist next to the liftgate handle and try to open.

I also have a '96 Grand Cherokee, and i had the same problem with the rear liftgate. If you can get into the back trunk space, take out the screws on the trim panel, once you get those off, take a 2x4 or something to hold the trim panel out. Reach your hand down there and if your on the inside the latch will be to the left, just push it down and the door will open, once open you can take the rest of the screws off and see waht was wrong. On mine, the latch was just seized, so i sparyed some wd 40 on it and it works fine now, except for the flipper glass, im not sure about that.

Did your sound quit working after or before you put in the radio.