No, if the fiber washers were in there as shims they should stay in.
And even though the bearings are allegedly "sealed" they are cheap
insurance to give the crap one more barrier to get past.

 The only other 'maintenance' thing to do while it's apart is to
change the brushes.

 If it's more than that let the generator shop handle it.  Because
they have the tools and test gear to test the components while it's
apart, and they should stock the regulator, replacement rotor and
stator windings, diode bridge, output studs and insulators, and other
bits that might need changing.

 They buy the replacement parts in bulk, and get a decent deal.
You'd go nuts tracking a source down, or have to pay /way/ too much to
a supplier willing to sell you just one.

 --<< Bruce >>--