As stated previously check out the Tiffin RV Network.
I recently purchased a 2007 Allegro Bus and was able to get valuable information from the forum prior to purchase.
Make sure you read up on the what the call the Big 3 Issues which I think the 2008 Phaeton could have. (Wetbay, Roof Rails and Driver Side Slide)
My 2007 had the wet bay issue which I was able to get repaired at no cost to me even though the coach is seven years old. Tiffin is fixing these issues for up to eight years after build date. I made arrangements for repair prior to purchase (locally) to make sure I was covered. When I did my research the driver slide issue requires a trip back to Red Bay the others can be fixed by approved repair shops other than Red Bay.