If the generator is on a slide, not bad to access, just go ahead and have it replaced at the next LOF change service.
If it is not on a slide, which my 04 Allure is not (And maybe the 05 too?), then yep it can be a PITA and expensive process. The shop I worked with back then, had to drop the generator out of the coach to obtain access to the generator. (For other reasons, but had the belt replaced at that time too.) If you do have to drop the generator, go ahead and have more preventative maintenance done at the same time. Flush the radiator, thermostat, temp sensor along with the belt. And personally I recommend either a Gates or Cummins/Onan OEM belt. Most belts are pretty good now days, but due to the costs of dropping the generator, I did drive out to Cummins and picked up an OEM belt. And I also had my coolant changed to Final Charge, at the same time I had to replace a clogged up radiator (poor maintenance by previous owner). I run Final Charge in the ISL engine, so that makes it carrying one coolant for top off's a bit easier
Best of luck to you!