Hi Ho: Diesel generators (like everything else in your coach) need regular maintenance. They need (at least) the followsing: oil change, coolant check (or change), oil filter replace, replace fuel filters (Tiffin has two), don't know about your coach, replace air filter, clean spark arrestor, check cables for tightness and clean if necessary.
You can get info on how to do these things or just take your coach to someone who knows how and hope they do it right. How often you need to do these things depends to some extent on how many hours of operation the generator has, but most suggest maintenance yearly.
I wouldn't worry about output frequency (Hz) since this is controlled by the electronic circuitry and doesn't normally change.