A homeowner can safely handle a few things on a mid-90s door: lubricating rollers and hinges, tightening loose track brackets, replacing a worn weatherstrip at the bottom panel, or reprogramming a remote when the opener stops answering. None of that needs a call.
What you shouldn't touch is anything under spring tension. A torsion spring on a double door built to 1990s specs is wound tight enough to break bones if it lets go while you're working on it, and an extension spring under load isn't much safer. If the door won't open, or opens partway and stalls, or the cable on one side looks frayed or kinked, that's a call, not a project.
We'll be straight about the one limitation here: if a part on your door is discontinued or the opener model is old enough that the manufacturer's stopped supporting it, we may need a day or two to source the right piece rather than fix it on the first visit. We'd rather tell you that up front than promise a same-visit fix we can't back up.