We sold our motorhome through PPL within a month and were extremely satisfied with the transaction. While there we were very impressed with the amount of traffic coming through - lookers, buyers, sellers and those picking up their RV. Everyone we dealt with were top-notch - no pressure.
Here's what they have on the lot now. It changes daily. There's a section on this site for diesels and gas. Check them out.
Just like any used vehicle lot or for sale by owner you'll find owners who don't care about their RV and it shows. You'll find other RVs in excellent condition.
http://www.pplmotorhomes.com/diesel/diesel-motorhomes.php