If you are that "far into it", I would think about replacinging the rear main seal.......with everything out you will be looking right at it

Yea, you have to be careful to seat it evenly and not all the way down but it isn't that bad IMHO. The hardest part, in my opinion, is finding/making the right "tool" to push that big old thing in there evenly....I don't do this for a living so I have to get creative on making/using a tool for things like this.....a block of wood, a piece of pvc pipe, ect.

Again, just my opinion on the rear main, many will let it "ride" if it is not leaking already.

 

You are correct in changing out the seal when it's all apart. Poor economics to do all of the work of pulling the tranny and leaving a potential problem unattended. I'm going to check for the seating tool that is mentioned. I have a friend who is a mechanic he may be able to locate a tool.
Just ordered a rear main seal, Sachs flywheel, and pan gasket. Once I button her up, I should be on my way to another 200K+ miles.

 

"Seal drivers" can be bought.....or made. If your friend does this type of work he might already have a tool. Me, since I do not do this for a living, I get creative. I can't even tell you all the different things I've use to seat seals.

Example, the last rear main I did (3rd gen, while doing a clutch job). Since I knew I was going there - car had +170K. I took the new rear main to at guy a work who was into wood working and he made a "driver" for me out of wood using the new seal as a template. So somewhere in the garage there is a piece of wood with grooves cut in it

These days, you might check you local parts stores, if your friend doen't have something already, they may loan out seal driver tools (you put money down, use the tool, then get all of your money back when you return it).

 

Maybe even a really big fender washer. Large enough to prevent pushing the seal down below flush with the surrounding metal.