I'm not saying that the shop's fees are unreasonable, but I don't see anything on that list that is particularly difficult for an owner with some tools and ability to follow instructions.
IF you want to do some of this on your own, it is all covered multiple times on the forum. You just have to find the posts or ask for help after searching.
The brakes on the 986 are the easiest I've worked on out of all the cars I've owned. Water pump is not difficult, but you need to pay attention to things like a bolt being longer than others and not gumming it up with sealant. Changing wiper blades? Sounds easy, but a few of us have cracked windshields by accidentally having the 'un-wipered' arm fall against the glass. It's all written about and done by many that were pretty new to DIY.
Take a look thru some of this:
https://www.pelicanparts.com/boxster/boxster_tech.htm
DIY Projects
https://sites.google.com/site/mikefocke2/mikesporscheboxsterwebpages
Like books? get the 101 projects book and Bentley manual
Nothing wrong with paying a shop, but labor and shop costs add up and they will stick with known reliable parts rather than look to cut costs to save you a buck or two.
If you are looking at paying the full cost of restoration by a pro, you will be 'underwater' with this car - you'd be better off selling it as-is and buying another. It's a free car, what do you have to lose by diving in and learning to fix it all yourself?
*Disclaimer* If you do decide to do it all yourself I accept no responsibility for any damages caused, or financial loss. Safety glasses, gloves, and hearing protection for small children that may hear your utterings are highly recommended.