O2 sensors are easy peezy. A sensor removal tool (Autozone, $12) makes it fast too. Do all four though, and find bosch replacements cheap at
www.oxygensensors.com. I paid $125 each and it took about a half hour in total.
Much better performance and fuel economy after I swapped them out.
Not cheap, but any boxster with 60k or more on it deserves new ones in my opinion, even if you have no CE lights.