Greetings from the Florida Panhandle
First off, welcome to the Forums. We're glad to have you with us.
As to your question as to the value of the 2006 28 footer, it's hard to say. A lot depends on condition. Assuming it is, in fact, in excellent shape, the value will probably be greater than the amount you will find in an NADA Book.
You should start researching Ebay, RV Trader, and the Classifieds here on these Forums. You are probably looking at $35M or more.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)