Wait, you said the shop pulled the heads and determined it was valve seat - they were 90% done if they pulled the head and put it back! If it was just a valve issue, the hardest part is the teardown to get the heads off IMO. I hope they didn't quote $2000 after doing all that, b/c really they did most of the work minus the send to machine shop part.
But yes, you can certainly do this without pulling the motor as indicated above. Searching for Headgasket threads should give you what you need. I've been outlining some of my experiences with that job in this recent thread: http://www.jeepforum.com/forum/f310/...haust-1450874/
You may not be doing a headgasket specifically, but for pulling a head the discussion is probably similar.