Rebuild Or Buy New(ish)

If you can't find a used one dirt cheap...and by dirt cheap, I mean consider the cost of complete rebuild plus whatever you're paying for it and weigh it against the cost of a replacement unit. Or, if it turns out you don't trust your own skills to rebuild your current one, I'd suck it up and buy a rebuilt one from a reputable vendor (D&D, Astro Performance, etc).

I've seen more junk used T5 sold out there, than I've seen good ones. Let's be honest....the only reason people tend to replace them in the first place is because they start to give them problems, or because they've blown them up completely and need a tougher unit.

And I wouldn't suggest a novice try rebuilding one on their own. It can be a daunting task and you might just end up with a pile of scrap metal you're unable to put back together in the end.

If it were me, I'd pull the stocker out and sell it as is, with a description of the issues (sound like little more than worn synchro's) to recoup some of the cost of buying a new/rebuilt unit. You probably won't have to shell out more than a few hundred dollars and the piece of mind and no stress level alone would be worth that to me.