You should have the cover on the bell housing, as dirt can get up there to the front seal.
What exactly did the shop do to your trans? It looks like the transmission was not removed, due to all the grease and grime on the bell housing. Even the trans mount bolts are dirty.
I hope they didn't just chuck some Trans Stop Leak in it with fresh oil and charge for a seal job.
It is pretty dirty looking trans..
NO. Oil sealer trans stuff is a myth...however, I did put some Lucas Auto Trans gunk in the auto of my old work van.
Holy crap, went from dodgy to like a brand new transmission in a day. Still leaks, but goes good.