98 GMC jimmy Trans prob dont know what to do.

Need some feedback on trans prob dont know what to do Help plz
Ok trans in our 98 jimmy has had this converter comming on and off at 40 to 55 mph. took it to the dealer and they confirmed it was the converter going on and off. They just want to replace it with a cert for $2500 If they rebuild it they say that they might night find otu whats wrong with it. From what i have been reading its the valve body. They say it could be a warn clutch pack or bad drum or focked converter. I told them to not fix it and I would drive it till it got worse. Really what should I do? 700 800 is not in the checkbook right about now.

Valve body is 79 bucks from what i have seen on a website. So I guess figure 100 for that. Should I start by replaceing that? Or what should I do.

Kinda need some idea b/c something will have to be done sooner are lata.

Don't try to fix a messed up trans, it isn't worth the money or aggravation, it will just end up being a money pit.
Go to a wrecking yard and get another good one, smell the fluid to make sure it doesn't smell burnt and is not brown looking, and just swap the whole thing out.