At a guess you’ve blown some output transistors, drivers and emitter resistors, $100 approx parts.
Looking at the dismantling layout, they didn't make it easy, the whole board has to come out. A good 4hrs labour, $400+ approx, in Australia some charge $150aud pr hr
https://www.hifisentralen.no/forumet/attachments/d652efdbaf5de7acb016cfb15c7350e9-jpg.619705/
https://www.hifisentralen.no/forumet/attachments/26d69d1d38275e8c54ccc5e8c030d563-jpg.594604/
https://www.hifinews.com/images/419unison.top.jpg
Cheers George