Replacing a wall switch or a set of safety sensors is within reach for a reasonably handy owner - both are low-risk and don't involve the spring or the door itself. Reprogramming a remote or a keypad is usually a five-minute job with the manual, if you still have it for a unit this old.
What we'd stop you on: opening the motor housing on a chain-drive unit, adjusting travel limits blind, or working near the door while it's under spring tension with the opener disconnected. On a unit old enough to be original to an 1985-built house, the housing itself can be brittle, and a stripped gear you try to force can take the sprocket and chain with it. If the unit hums and won't move, that's a call for us, not a screwdriver - past a certain age, guessing costs more than the visit.