I'm not sure what your mods are, but as long as you are running the stock upper intake the 70mm TB will be a waste of time. A 65mm will be more than enough, the intake is more of a restriction than the throttle body. Even if you are planning more upgrades down the road, the 65mm TB may still be enough. It takes a fairly serious HCI 5.0 to actually need a 70mm TB. I'm not sure if the 70mm will actually hurt performance or not when using a stock intake. But, it may however if the opening on the intake is not as large as the one on the TB.
As far as the TPS, yes you'll have to re-use your stock TPS. The IAC may or may not be necessary depending on what kind of condition yours is in. If there is nothing wrong with the current one, there is no need to replace it. If you are having any type of idle problems currently however, you may as well go ahead and replace it.
The EGR plate is necessary for the same reason the TB is necessary, more flow. The aftermarket EGR plate will have a larger "bore" than the stock one to match the TB.