1991 Corolla GT-S Electrical?

Hi, I have a 1991 Corolla GT-S and there are a few things a little quirky about the car and I was hoping you guys could help me out.

When I press the lock button on the driver side door, the passenger door doesn't always lock. Sometimes it does (rarely) but usually the switch just twitches, but doesn't fully lock. I'm wondering if it is an electrical problem or if there is just something in the way of the mechanism behind the door panel. If the latter, could someone help me in removing the panel. Any suggestions would be greatly appreciated.

Also, the car's speakers do not work. The audio system is stock and the tape/radio receiver seems to be working fine. But the speakers don't get any static or noise whatsoever. Could it be a fuse or is the wiring faulty? Is this a known problem?

Then there is the passenger side view mirror. The driver side view mirror works fine when adjusting, but the other will not adjust using the electrical adjustor. It must be done by hand.

The final thing is the sunroof. The previous owner said that it needs a replacement belt, but those can only be obtained by buying the entire motor assembly. Is this true? Where can it be bought?

Thank you very much in advance.

I was able to, with a friend of mine, to get the passenger door lock to work. After taking off the panel, we found a plastic guard that was causing unnecessary friction in the control arm of the latch. Once that was remedied, it has been working fine. Can anyone help with the other problems?