I would probably want to see more pictures of the overall condition and what, if any, accessories are included (ie, hoses, WDH, etc.), as well as the type of tires and battery they had put on. I would also want to know about any mods they have done. There isn't a lot of specific information in their ebay post and 5.5 hours drive ain't no hop skip and a jump away.
Price wise, that's not too shabby of an offer. Your not trying to get it for a steal, but it's still a pretty decent deal if it's been well maintained. I probably would offer more like 8000. You can always increase your offer, but you can never go back down unless there is something noticeably in need of immediate attention. I would also want to find out about any warranty or dealer repairs that have been performed and ensure the registration has been kept up to date.
IMHO, 2006 is getting a bit borderline. If it hasn't been well maintained tanks can start getting a little brittle, slide motors and pumps can start failing, caulking and seals could be in need of attention, etc.
If the floor plan fits your needs though all the more power to you. Hopefully the feller would be prepared to spend a couple of hours with you and test all the onboard systems. If not, I would probably walk away from it.
Good luck and Have Fun!