BMW Repair: Left rear Door, electric door locks, door latch

Question
I do not have a mechanical question but more on the line of body work.  I have a 1989 525i BMW the left rear door will not open.  Vehicle has electric door locks.  I have tried to unlock the door by pulling up and down on the door lock plunger up or down.  Took off door trim and tried to pull the door latch cable by hand, cable did not move.  

Is the door lock frooze or rusted?
If I disconnect the battery cable will this free up the electric lock?  Does make sense to, just a thought.
How can I or whan can be used to access the latch and trip it open?  I will prefer and not have to pull the inside panel off.  I feel I may damage the upholstrey.

Thanks,

Vic Vaughan  

Answer
Although you may feel that someone might damage the interior,they may not.I say that because that is what i do,I repair other peoples problems due to them not being able to or wanting to.Having someone who has done it is better than doing it and causing more problems.If you want to do it your self and have ahd some experience in panel removal I would buy a manual (Bentley) and check out the steps involved. Good luck