Reusing that UIM is fine, I'd soak it in something like a cheap 33 gallon trash can, and some de-greaser like purple power, when you remove the throttle body gasket be careful, the ribs/groove on the UIM that holds the TB gasket in place broke off a bit on me, as it was softened up from all of the heat cycles I guess, so I had to replace the UIM, if yours is fine they UIM Kit will work fine.
If you do have to replace the UIM the Doorman Part # 615180 will work, it is what I used, some will get the ineedparts one that has some extra security added to keep the EGR port from warping, I have found that replacing the EGR stovepipe with the one you will get in that UIM kit keeps the gasses from warping the port.
I'll give you a link to the Kit I am talking about, in case any others read this thread, and are curious about it.
GM Intake Manifold Kit
That T-Stat should be find, it will be a 195F stat, I drilled a small 5/32" hole in the 12'oclock position of mine to help with the bleeding of the air, if you do not drill the hole to big you will not have any issues from doing so.
You could replace the thermostat during summer/winter like Mike suggests, but it is not necessary.
One thing I do not see in that kit is a paper gasket for the thermostat, I know the rubber one goes around it, I used that, but rather than just use a little rtv I opted to use a paper gasket that came with the LIM kit as well, and coated it with a little rtv, not sure using it was necessary, but I just felt better doing so, and I have not had any leaks at all, you really do not need to use rtv on it as it has some on the gasket that will work, but I like the added piece of mind.
Since you have the Prestone fail-safe thermostat already in there you may just want to reuse it, and keep the one you get in the UIM kit as a spare.
All of your parts listed sound good, while you are at it clean your TB and butterfly valve good, mine had lots of carbon buildup.
If you have any issues let me know and I'll help you out.