Yes, avoid like the plague!
I had Freddie Krawiec at TransTorque do my '86 GN trans in 1990 (rebuild/Transgo shift kit). He was local and had a really good rep with racing 'glides and TH400's. Big mistake, he knew absolutely nothing about the 200R4 back then and I doubt he knows about them now. I should have taken my car to Pat Barrett (Level 10) and been done with it.
If you're looking for a good trans shop in Central Jersey, I suggest Eric at Dynotech.