[AKnowles]

As an owner of a 99 Boxster base the first thing I'd suggest you do is get a CarFax if possible so you can see if any service was performed regularly. When I bought mine, that is one of the key indicators I looked for and could see the original owner and the next kept up the maintenance. The next two didn't show any service history, but both drove below average miles. I was somewhat concerned about it, but decided to just enjoy the car and do my own maintenance. So, far I've had two oil changes and both show zero debris in the filter. Since I have a dual row bearing (assumed since it's never been apart) I have decided to replace it each time I replace the clutch.

If you are really concerned about yours, drop the oil pan and check it for sludge, debris, etc. since most times that is where you will see a real indication of potential issues with the engine.