904 shift shaft seal

You may not like my response. I went to the effort to drop valve body and reseal the selector shaft. Approx' 90 days later the front seal at torque converter started leaking. One might blame the 6 quarts of new fluid but... all these seals are the same age.
Five garages quoted the same 400 USD to replace that seal and also insisted "complete rebuild is the wiser route", more or less refusing the front seal R&R job.
My 67 model 904 was rebuilt in 1984.
How long since your 76 model 904 was rebuilt? That's the 1000 USD question. Good luck.