You don't say what year the 28A is. That makes it a little hard to estimate.
1. Unless you have a reason, waste of money.
2. Age? How many hours on Genny? How does it run now? Probably wouldn't do anything.
3. Age? How does it run?
4. Check the DOT date. Replace if over 6 years. Some may say fewer years.
5. Age? How does it run?
6. Age? Not a bad idea anyway.
7. Have the battery load tested. If you plan on off grid camping add batteries or switch to GC2 batteries.
8. Age? Mileage? How do they look? How nervous are you?
Seems to me most of these are a waste of money unless you have a reason for spending all that $$$.
