Try not to be tempted to drive a screwdriver between the old seal and the case. You can easily damage the soft aluminum.
I say this merely as a precautionary warning - definitely a "do as I say, not as I do", because that is exactly what mine came down to on a replacement gearbox I purchased last year. But by the time I got that nasty, old seal out of there, it was obvious I never would have gotten it out any other way, short of opening the box and pushing it out from the inside. It is an older gearbox without the external reinforcing ribs that all R65s have, and it was either the original seal, or it had been ridden in a LOT of rain. The internal steel ring of that seal was rusted quite thoroughly.
I haven't put many miles on mine, so far, but I think it is holding...