First off , Welcome and congrats. Don't let this minor setback get you down as once you catch up on some minor maintenace you rarely see problems.
I would guess it's the dreaded ignition switch. Especially if you have any trouble taking your key out or if it doesn't automatically turn back to the run position. Good news is, its an easy fix and only cost around $35. You can easily, ok moderately do it yourself. Go to the DIY thread on here and look for the ignition switch replace thread. I did it and found some sort cuts. Takes about 15 minutes and it really takes no technical expertise.
http://www.987forum.com/forums/showthread.php?t=21844
I have a 2001 "S" and I know the 2002 are identical. If it hasn't been replaced, it will need to. If that doesn't fix it then no harm done as it is a must on all older Boxsters.
Oh you can order the part from advanced auto parts for sure and probably auto zone. Check out pedros site and you will see most everthing short of engine rebuild can easily be done in your garage with a jack and some stands.