Wow, that is extremely low mileage for a '98. I hope you have been doing annual maintenance. Letting these cars sit can be worse than putting a ton of miles on them. I would definitely do a full inspection of the car, especially anything rubber or flexible that could have hardened (coolant hoses, serpentine belt, etc). When I purchased my '99 in '07 it had gotten less than 2k miles per year, and I had some initial issues related to the car sitting around too much, like fuel that had crystalized in the fuel line.
You can find a recommended maintenance schedule here:
Maintenance Schedule - Porsche Boxster (986) FAQ