The suspension seat adds about 2" and requires moving the seat belt to the seat instead of the body. I just took my seat belt off (don't tell anyone) it rubs the sides of the seat with the suspension system. I really like the seat, I would say it is worth getting.
You didn't say if you got the bagger. If you did you need all the front weights with the DFS.
The throttle shaft is pretty simple. There are several how to's on here. A good screw driver that fits the throttle plate screws is important, they are tight. I would mark the plates so they go back in same side and direction. Install the screws and let the plates close to center them in the bores and then tighten. I would recommend locktight.( you don't want them coming out).