Location?
tapeheads.com has several techs who repair R2R.
Of course, there is a huge lead time for the most respected techs.
The moderator, 'Pacific Stereo' is in LA and though retired professionally still does restorations.
There are a couple of East coast dudes and a Nashville guy as well.
You have to request to join [fill in a short form], but it is free and they usually reply within 48 hours to admit you.
I bet He has not ruined it unless he went crazy. Improper demagging will result in several issues.