I have had problems with the drivers door lock on our 87. Have you gently pried off the chrome cover? If not, use a small flat blade screw driver inserted into the key slot and see if you can get one side off. That will then let you have better access into the lock and you can look for the door and spring inside the key slot. You might try a needle pick (you can get a set at Harbor Freight or Lowes also has them) in the key slot if you see something and try working the obstacle out. If you don't see anything, get a spray can of solvent (brake cleaner) and use the straw and spray a lot of solvent into the key hole to clean the insides. Put a rag under the lock to catch solvent/grease as it flows out of the lock as you solvent wash the key hole. While there is solvent in the key hole, insert your key and gently work it to see if you can get it completely in and if you are successful, then gently turn it to see if you can get it to lock/unlock.

Good luck. I kept putting the cover, door and spring back on when the door got out of whack, but eventually gave up and it is now cover less. One of those things to get at the pull a part one day.
Lee