A while back, I sold the door gaskets from my parts car to another forum member. It may be hard to find someone willing to sell them because it makes the rest of the door harder to find a home for, but I'm sure you can get a good set if you are willing to pay.
http://986forum.com/forums/boxster-parts-sale-wanted/57559-wtb-door-seals-both-sides-inner-outer.html
My price in that thread was sarcasm. I charged a little over shipping cost. Of course, a business will have to charge quite a bit more.
I have replaced the windshield in two Boxsters. First time, I just took it to an auto glass shop and paid around $325 for a new windshield. Next time, I took my parts car to a shop and had them cut out the windshield, then install it on another car - $80 for the labor.
http://986forum.com/forums/general-discussions/60356-diy-windshield-worth-try.html