Depends on the dealer. At cochran we have 3 tranny guys. One does the trucks and the other 2 do the cars. Both of them have been doing it for years and rarely have come backs.Im not a mechanic but just from working around in the shop a shutter at low RPM in between gears sounds like a torque converter.just my $.02.
also make sure you make a note that the tranny has to be hot or like you said request to ride with a tech.