With regards to the shiny steering wheel/mileage thing, I'll bung in my two penneth!
I have done nearly 48k in my PD150 and the steering wheel still looks brand new. That said, I have VW floormats fitted to all four footwells, and the drivers one has a hole in it, and has done since about 25K, so I guess interior wear will come down to the specific user.
if its a 99 its surely only just come out of warranty, and (I would gues) have a full dealer service history. Can you not trace mileage through this?