[KevinH1990]

I'm assuming that you are from Jersey in the UK, not New Jersey in the US. I do not know the UK market well, but it seems that Porsches are more expensive there. Many Boxsters are on the market in the US now that are in near perfect condition at reasonable prices. Like the previous poster, I would probably pass on the car you describe if it was for sale in the US.

To answer your questions:

The oxygen sensor is a fairly inexpensive fix if you can do it yourself. The rear window can be replaced, but it is probably not something you would be able to accomplish because you need a heavy duty sewing machine. Sewing in a new window will cost $300-450 if you can find someone to do the job. Many people replace the top with an aftermarket glass window top. That is about $1500 in the US.

I have not had a problem with the seat mechanism, so I won't comment on that.

Here is a good compilation of information on the Boxster:

http://mike.focke.googlepages.com/mikesporscheboxsterwebpages

It describes the oxygen sensor and top repairs.

Randall Neighbor - a frequent contributor on this board - has a good page too.

Good luck.