Actuators will be fine. The grease in the door latch mechanism has long since turned into a heavy wax and collected dust. The fix is to clean out the latches and lubricate them. This can be done many ways, but the easiest / cheapest fix is to hose the latch mechanism with a can of brake clean and spray it with a lubricant that disperses well.
When I work on trucks this old, I end up taking the door apart, and removing the latch to wash it out in solvents, and replace it if it's worn after a thorough cleaning. Lubricate and install.
YMMV, but most of the time this is the best way, as it's impossible to get the latch perfectly clean without removal. An old toothbrush or stiff bristle parts cleaning brush works best to assist cleaning in solvent.