I was nervous about nicking the crank, so I pulled the oil pump in order to replace the front main seal. Piece of cake.
Along with every other seal on the back, bottom, front and sides of my engine (save the aforementioned front main seal) I have to replace my rear main seal. I haven't seen it, but it's likely got a metal ring inside the rubber, so drilling a hole in it and pulling it out with a hook makes sense; you'd have something solid to pull against. It sounds way better than trying to pry it out with a screwdriver, anyway.
If you don't have any, get a set of picks from Sears. I use mine all the time.
http://www.sears.com/shc/s/p_10153_1...0070921x00003a