Hi Schmidtlap,
I think there was a production change to protect the edges of the slide out floors from water intrusion. If the unit you're looking at doesn't have any damage, all you need is to make sure the edge is protected with a strip of metal or plastic. If it does have damage, a good repair is essential.
I don't know if it was on 2008s, but I think there were some Lippert suspensions that had problems. If this unit has MorRyde, you're probably ok.
Check the condition of the tires and make sure they're not more than 4 years old and have no unusual wear.