Originally Posted by 79pmooney

Are you prepared to admit you've failed badly and take the mess to a bike shop? If you dive in. this might ultimately be your best bail out.

Now that said - I like that you want to dive into this. So some hints. This wheel wasn't always out of true. Something changed, Spokes don't self-tighten. They may well have been built up overall too loose, but no spoke up and tightened itself. (A previous owner may have.) So 1) look for loose spokes. I like to pluck them and listen for ones with lower pitch or simply a thud sound instead of a ping. When you find a loose spoke (or one with a much higher pitched sound) look to see if the rim moves away from the loose spoke or towards the tight one. If yes, you may have just found the problem. Adjusting that spoke to the sound of its neighbors may return the wheel to close to true. If so, hurray! But - the spoke may be loose because the rim is bent toward it. If so, tightening it will make the wheel true worse.

If the issue is one or two lone spokes loosening, you may be able to make large improvements just correcting them. If it is a bent rim issue, well correcting a bent rim with spoke tension makes the overall uniformity of tension a lot worse. Better to accept that money needs to be spent on a new wheel of a rim replacement and rebuild.

In the meantime, get a good wheel building book. I like the book "Building Bicycle Wheels" by Robert Wright; long out of print but not hard to find on-line. He keeps it simple. (Was also a very good, in demand local wheel builder for the Santa Cruz racing crowd circa 1980. None of the principles have changed since then.)