Jarat1, since you are looking at used units, the number one Uno is 'maintenance' !
Holiday Rambler is a Monaco sister product. If it were me, I would stick with a Cummins or CAT engine and not go with the Navistar engine in the Holiday Rambler line if they used them (but, I'm thinking it would be a Cummins as a 2010 was built in 2009).
My brother had a 2005 Damon Astoria that was an entry level diesel. Gave him no unusual problems. He is now on his second Tiffin product.
Remember 'maintenance'!
Safe travels,
MM.