Valve body clunk

[tarmon8r]

99 yukon denali. Transmission needs the valve body fix. It does the ole short shift clunk 1-2 and 2-3 at low speeds. However, we were on a long trip in Pa, going up those long mountains not hauling anything but the temp outside was blistering. Cruise control set at 74 and about 3 hours into the trip, the tranny slipped out of gear. Pulled over and looked under neath. Tranny fluid everywhere. No obvious leaking like from a broken line. Filled the tranny back up with fluid and not a leak yet(3 months later). I think it overheated. Went to AAMCO when we got back.They "pulled the codes" and said the trans needed rebuilding cause the code said trans slipping and the seals were bad cause of all the fluid under the vehicle. (bullsh*+) Well three months later, no issues, no leaking except for the clunk shifting. Any and all insights are appreciated. I would like to get that valve body replaced. Where can I purchase it? Part number? Even if I cant do it, even though i have a very good idea of how to, i would like to tell the mechanic exactly what i want done and not just some random donkey valve body.