Okay, didn't feel like trying to take off the speedo housing (thought that there might be another gasket to have to replace if I did that), so I just drilled two holes in the seal, cranked in two sheet metal screws, then used a claw hammer to pry the seal out. Worked like a dream. I guess I still don'd see how you get a seal puller in there with the shaft in the way.
Getting it back in I tried first to cut a hole (smaller than seal, bigger than splined shaft) in a piece of plywood then set it against the seal, then set a pipe bigger than the shaft against that and bang on it. Too many things to hold up, so I ended up just really carefully tapped around the edges like Jeff said, just like wheel bearing seals.
Sealant on the splines of the output shaft before putting the drum back on? Didn't know I had to do that, figured the seal would stop any/all oil from leaking out?
Anyway it's basically back together, might have to dive back in to seal that if it's necessary. I hope that stops my leakage, I'm sick of adding oil to the t-case every few weeks...