Anyone give me advice on installing a new overdrive rear seal in-car?

Looks straightforward enough. Remove the drive shaft. Use air tool to remove the retaining nut, pull out the coupling flange and remove the old seal. Fit the new seal and refit the flange and nut, tightening to 80-100 ft/lbs.

I know it can't be that easy. Will i need to use a puller? Anyone have a new seal or know the seal number? Planetman? Or should I just pull the old one out and go to the seal store? Somebody tell me what I'm in for. Got the car up on four jack stands to bleed the brakes, so might as well do this now. That Redline tranny fluid that it's leaving on the floor is expensive. BTW, it's the rear seal, not the speedo drive that's leaking.