Hi Gary and Oliver,
Per my earlier post, (to Gary's 2 questions) 1. the rotor is bolted to the flywheel and is self-supporting. The end frame with its bearing is, of course, needed for support when the genset is running. 2. The bearing will slip in an out with only, perhaps, putting the new one in the freezer for awhile before inserting it.
And, Oliver, as to a procedure for checking the generator bearings for wear, I am unaware of a procedure for that and think you really want to replace it after the hours recommended in the manual (if I recall, it's 2500 hours). One really doesn't normally check bearings for wear - it is a preventive maintenance item and you really want to replace them before they wear "too much" and cause damage to other components.
This is not brain surgery - it is a simple DIY task that doesn't need a paid mechanic, unless, of course, that's how you choose to maintain your boat.
Good luck with it,