Hi,
1999, 4 door sedan passenger side doors dont work wither from inside the car latch or using remote control.
Some times the front right side works when the back one is locked and some times wont but the back right side door lock will not work at all.
Please help me find the solution and repair it by myself if possible.
I am not sure how to open the door panel to see whats wrong.
Thanks in advance

Sounds like the switch might be touchy, you'll probably have to replace it. To get the door panel off there should be a screw inside the door handle and then you can just pull the panel off (there's plastic clips on the back of the door panel, you might break a couple pulling them off).

May be the window control box. You may need to replace that.