First of all, I could have my terminology wrong but I thought the "stator" coil is mounted to the inside of the cover. The "rotor" is mounted to the end of the crankshaft. The rotor, and rest of the alternator, sits in oil and there is no seal behind it. There is an oil seal on the other end of the crank by the points. You don't have to remove the rotor to change a seal or crack the case. It just makes reassembly a little easier but not much.
You do want to remove the gearshift mechanism. Still no oil seals that I am aware of but if memory serves, you wouldn't be able to remove the transmission unless you took off the gearshift mechanism. Take lots of pics while you do that. Will make reassembly easier.
What oil seals are you referring to grcamna?