There are a few key maintenance items that should be done as a boxster passes the 60k mark, but if you don't have complete records on the car, you might be replacing things that have already been replaced.
Spark plugs are usually changed by 60k (cheap). O2 sensors are recommended to be changed out at 60k, although many boxster owners just wait until the car's ECU throws a CE light and then all four are replaced (replacing just the failing one can make the ECU go haywire). These are not cheap. $450 a set, but the job is an easy DIY job taking 30 minutes max.
If you have no record of the car having the radiator overflow tank replaced, do a visual inspection by removing the carpet in the rear trunk and the floorboard wood and see if any radiator fluid has accumulated down there. If you see fluid, make the dealer you bought it from replace it. It's expensive.
My web site has some other stuff that will help you. You should also visit
Mike Focke's pages ... his web site is simply a wealth of information.