Hi Matt,
I used a 1.5" PVC coupling and a small rubber mallet to seat the left main seal. You should be able to get the old seal out without splitting the cases. I've never done it without splitting them but that's because I've always had to split the cases for other reasons and just replace seals while I'm at it.
Just thinking out loud here but you could probably run a couple of long sheet metal screws into the existing seal and then attach something to these to pull it out. If you can get long enough screws that reach above the end of the crank you could put the stator bolt in the crank, use a piece of flat steel over the bolt head and span across beyond the sheet metal screws. Drill a couple holes in this plate, run the screws through this and then into the seal. Now if you wrench the bolt out it will push against the plate and *hopefully* pull the seal out.
BTW, my engine has been holding 10PSI for over 10 minutes now. Think it be good to go.
HTH,
Loren