Congratulations!
The best mod you can do is what bmusatti mentioned in another post somewhere, buy a melon protector (AKA a helmet) and go run some autocrosses (PCA or SCCA have a bunch every year). I don't think there is a better way to safely take advantage of what Porsche designed into the Boxster! After you get some driving under the belt and do a ton of searching this forum, you'll be able to really understand/appreciate the mods available for this car.
