Had to do that years ago, a little time and it worked like new.I had the same problem with a late 90's Riviera. I rolled down the window and sprayed WD40 on the door linkages from the lock assembly area to the area of the interior latch. Continue to work the linkage as you spray.This did the trick for me.
And hold your tongue in just the right positionSometimes it helps when you pull the door lock pin firmly up, while you simultaneously pull the door handle (either from the inside or from the outside).