I don't know if you noticed, but this unit has some fairly obvious damage to the front section around the front window. The seller describes this as "hail damage" but if that's true it must have been some b-i-g hail.
If you like this trailer, it would make sense to me to get a proper quote from an AS dealer who is active in doing this sort of repair before proceeding. I personally think the question people would ask about the damage would have you running to get it repaired before long...
It would also be a good idea to get a survey done on this unit by one of the Airstream Inspectors listed under the link of the Portal page. The you will have a very good idea of its value.
Good luck with your purchase!