First Boxster

[boxstershorts]

Get a PPI. Although it sounds like it may be to late?
Get a Carfax
Things you can check (leaving out the obvious and the stuff a dealer should check out):

Make sure there are 2 keys and all original manuals
Get historical paperwork
Try all gizmos and gadgets (specially roof deployment, AC, electric windows, heated seats, defroster, elect mirrors, pull on headlight switch ... twice, lock of center console, lock of glove box)
Are the wind deflector and roll bar inserts there?
Is the little tool kit complete behind spare wheel
Try all buttons on both key pads
Drive parallel to a wall to hear any weird noises (this is a great trick!)
Accelerate one wheel on grass, brake with one wheel on grass
Brake and let go of steering wheel...
...
Aesthetically: Check rim edges, windshield, roof, inner headlight lenses, rear window, leather seats, look under edges of car all around, callipers still nice?, wheel bolts rusty? (could be sign of winter driving...you don't want that)
...
I'm sure I'm forgettting something...

congradulations and welcome to the forum!