rear Main Seal noobie question

You don't need to remove trany,, you pretty much seem to have a handle on it..

BUT,, you need to be absolutely sure the oil leak is the rear seal.. Oil can migrate down from the oil sender/dist,, or leak from the oil filter/adapter,, valve covers,, fuel pump and along the pan to rear, with fan and gravity moving any oil to the back of the pan..

So were I you,, I'd wash the begeebees outta the engine with "brakeclean",, and then watch very, verry carefully to see where it's originating.. my $.02

hope it helps