Repairs Leaking seal on axle shaft.

I have a Craftsman zts7500. One of the hydrostatic transmissions is leaking oil. Looks like it leaked a cup full over nite, I had a time refilling it. Its leaking at the axle seal. This may be a sealed transmission, I don't know. Can the seal be replaced by a novice like me? I was a break & front end mechanic back in the early '60s but things have changed since then. Cambre