Anybody ever change a rear seal with the motor IN the car? Im talkin 2nd gen Camaro....

If you pull the distributor, fan, mounts, exhaust and anything else that restricts upward movement, you can pick up the engine with a cherry picker & have enough clearance to pull the pan.
Other than the tranny mount(which you might have to loosen anyways), bellhousing bolts & converter, you're 99% of the way to removing it anyways.

I personally would prefer to change a rear seal on an engine stand than be lying on my back fighting for that extra 1/2" of clearance you can't seem to get.

I'd pull the motor & have because of that seal.

+1 with the engine pull. Real pain, but you'll do a better job looking down at it working on a clean surface, rather than on your back, crammed under the car, trying to squeeze the new seal into place. How bad is it leaking? Sometimes you can get away with adding lucas or changing to a heavier oil/high mileage oil and the additive will help swell the seal a little, causing it to leak less or stop completely. My 80 3/4 ton truck was loosing a little, about a quart every 2500 miles, just enough to be annoying. Added a pint of lucas, thing swelled up nice, hasn't leaked since. Might not be a permanent fix, but its worth a shot, unless of course you want to pull the engine, which is fine to.

Its not bad at all. I have done it on a few occasions.

You dont need a cherry picker. Pull the dist so you dont break it. Pull the motor mount bolts, use a 2X4 placed under the oil pan and jack it up. Make sure you have it oriented to even the weight and not crush the pan. Once you get it lifted high enough, place small blocks of 2X4 between the motor mount and the mount brackets. Lower the engine and it will rest on the blocks. Than you can removed the pan ect. Reverse order and youre done

I did as badazz81z28, used a 2x4 to jack the engine...
And used this webpage as reference: http://www.corvettehacks.com/article5.html

Ive done the 2x4's also. Its still a pain in the ass changing it though.