David:
Ok, to see what's required, check out this pelican parts article (it's also available in the 101 Boxster projects book):
Porsche Boxster Cruise Control Installation - 986 / 987 (1997-08) - Pelican Parts Technical Article
With a 4-stalk, you can also add OBC (on-board computer):
Forum member pdwight had some excellent harnesses for the OBC upgrade, he might also have pre-made harnesses for the cruise upgrade.
Not sure what else you would need for the intermittent wipers... (others will probably chime in)...