I think those types of places, from many many accounts , are in too much rush to be counted on...
If you read alot on here after doing some good searches, or get a shop manual... you will know enough to do it yourself,,, or better yet, supervise some teenager in the neighborhood doing it correctly....
The last time my father took a car to one of those places... the oil plug fell out about twenty miles away... he shut down fast and called me.. so it did not hurt anything.... but he learned a lesson...

I am a big fan of Trans-X for keeping varnish from building up or cleaning it prior to changing out the fluid...
So I would take out enough transfluid ( two quarts ) and put two quarts of trans-x into your car. That may fix the problem by itself, if not it will dissolve varnish starting to accumulate... and it will leave the area when you change fluids.... Drive it at least 100 miles before the change.. give it time to work.....
I had a Ramber once that I bought for a song because the ONLY gear it had was second..... A mechanic friend suggested this stuff.. and one can FIXED it totally... I drove that car for 5 years... LOL... and since it had been designed by Pinninfarina... just like Mercedes.... I put a MB grille on the front.... LOL.. and many people thought it was a MB....

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