>>Oh, no! I noticed oil running (drooling?) out behind the trans. If my diagnosis is correct, what seal is it?

I presume that when you say “behind” the trans, you mean at the trans-case interface? If you mean literally “behind” it, as in out from the boot at the trans output, you can stop reading. If not, you more than likely have a rear main seal failure. That’s the seal where the crankshaft emerges from the case to marry the flywheel.

Tools?
Pitfalls to avoid?
Tips?
Other items to replace or rehab at the same time?

With the bike now up on an elevated table (we call it the “surgery table”) and with the final drive, etal all the way off, it would be a shame to take it to the dealer. Plus the $$$$$ consideration.

Then this is the IDEAL time to do it. You have to pull off the final drive to pull the trans anyway, and that is a big part of the labor. You will need a few special tools… a flywheel holder (holds it in place so you can unbolt and later bolt the flywheel to the crank), a set of three ( I think) longish metric *fine* bolts for backing off the clutch’s diaphragm spring, and finally a tool for seating the new seal to the correct depth.