Removing the old seal was a bit of a trick. If you have a seal that is easily accessible you can pry it out or drive a couple of screws into the face of it and use a claw hammer to pull it out (another trick that I learned from Dave). This seal was located deep down in a recess in the back of the clutch housing. Being located in that narrow recess prevented any prying from the side.
This job was a great opportunity to use a tool that has been sitting in the bottom of my tool box for years. This photo shows a seal puller that I bought at a rummage sale a long time ago. I think that it is actually made for pulling packing glands in valves or traditional rear main seals in engines, but I figured it would work fine for this job.
I drilled two small holes in the face of the seal to twist the little "cork screw" into. Then I simply alternated pulling on each side till it popped out. Once I had the seal out it was a simple job to tap the new one in and clean all the oily mess off everything.