RE: Transmission Cooler Install
I installed a Flex-a-lite part# 4232. I tried several of the smaller sizes (GVW ratings around 17,000-22,000), but they just didn't cut it at all (made almost no difference). Mine is rated at 32,000 GVW, and does a great job. I think the smaller ones would work fine if you bypass the radiator though.
That one you linked to looks pretty good. It is kinda small, but that's ok because it is thick. That combined with the fact that it is a plate and fin design should make it a decent cooler. Looks like everything you need is included.
Here is how I installed mine. There are other ways, but this has worked very well for me.