[Gelbster]

"can anyone recommend a parts vendor?"
Try Pelican because of good prices ,great service and outstanding diy info.
Here is an article relevant to the project you mention:
Porsche Boxster Spark Plugs and Coils Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article
Porsche Boxster Drive Belt Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article
http://www.pelicanparts.com/catalog/SuperCat/1048/POR_1048_BRKPAD_pg1.htm#item0
http://www.pelicanparts.com/catalog/shopcart/101P/POR_101P_BOX003_pg1.htm
Lots more just Google "Pelican Boxster +your project" or buy Wayne's book - no better diy book for the Boxster exists.