First off congratulations on your Boxster. I bought a '99 last May myself.
As for the factory workshop repiar manual, you can buy it from
http://www.my-porsche.com.
Part Number: WKD-483-521
986, Boxster (includes "S") 15 Volumes
$451.41
I have had all servicing done by qualified Porsche mechanics/dealers though.
Oil change, brake job and such are pretty easy to do on these cars, but I just don't have the time to mess with that, so I go the dealer route or qualified independent Porsche mechanic.