Surely someone knowledgeable will provide helpful information, which I can't. From the Google images I found, this is one of the drawbacks of a rear radiator design, which limits access to the engine compartment.
Our RV is also a 2012, and I share your concern for the condition of the belt. Fortunately, I haven't needed to use it yet, but I made it a priority to buy a spare soon after we bought RV, just in case. If/when one fails, you're dead in the water till it's replaced.
2012 Tiffin Allegro Bus 43QGP (All Electric)