agree, brake fluid every two years unless you track then it should be once / year
DYI costs:
* initially you need the "power bleeder" equipment and the catch bottles, around $80
* 2 liter of ATE super blue = 2 x $15 (you need just a tad more than 1 liter, so you need to buy two
* problem: I still need to find a place in the Bay Area who takes used brake fluid
pads:
well, when the "break wear light" comes on it's time to start thinking about changing them
DYI costs: rank from $150 ~ $400 depended on what kind of pads you want to use
rotors:
you need to measure the thickness of the rotors and compare it against Porsche recommendation, I don't have the values handy but should be easy to google
costs: around $600 for the rotors and you also need a few bolts ($40 ?)
If you have everything done at the dealer:
(wild guess) $2k ~ $3k
here are really good DYI instructions:
http://www.bombaydigital.com/boxster/projects/brakes/