Pelican Parts is the forum sponsor and has decent prices and good customer service. They also have a great collection of DIY articles:
https://www.pelicanparts.com/boxster/boxster_tech.htm Because of that I will often buy there.
I don't want to promote their competition, but I do sometimes find
very good pricing on some "manufacturer's closeout" parts at Rock Auto.
Woody may still have a few 986 parts remaining, but he has pretty much stopped buying salvage 986s to part out. For used parts, it is probably best to look through the classified section of the forum or post a 'WTB' for whatever part you need. I have two parts cars and boxes of stuff from a couple cars that I have scrapped. Although I'm not an active seller, there are people like me who will often reply when someone needs stuff.
There are some reliable eBay sellers. One of the best is
Quality Porsche Parts
European Parts Depot has been very good to deal with as well.
Manuals? The Bentley manual is probably the one that is used most. Often available here on the forum used.
https://www.pelicanparts.com/catalog/shopcart/BOOK/POR_BOOK_PORBK1_pg7.htm
I have the factory service manual which sometimes comes up on eBay for around $1,000 ...and I still often use
Wayne Dempsey's 101 Projects book instead.