My 2001 S has an inline fuel filter located about in the middle of the car. I changed mine this summer. They changed things in 2002 to a "permanent" one inside the gas tank.
The procedure for the early one is detailed in the 101 Projects book, or you can find it on the Pelican website here:
Porsche Boxster Fuel Filter Replacement | 986 / 987 (1997-08) | Pelican Parts Technical Article
Be careful when removing the old filter - it's quite large and holds a lot of fuel. Be sure to have something ready to catch the fuel. More will pour out as you remove it (you have to tilt it vertically to get it out...
Also be careful how you have the car jacked up. I jacked my car up and then set it down on tall ramps (too tall to drive onto). I trust ramps more than I trust jacks or jack stands. And chock the front wheels. You'll be under there for a while, so make sure the car can't fall on you.