Ok first off there aren’t any n/a FDs, no TT FCS just a 13bt for the FC which is a single turbo 13b. I'm not totally sure but I think the motor mounts on a 13bt or 13b are different then the 13brew. A FD shell is more then likely going to run you around 4-5k unless you're lucky then you might find a wrecked salvaged title FD for 1-2k but that’s still unlikely. As far as the gens go I like the second gen body the most but from what I've heard the first gens are the most reliable, but the FD is going to make more power stock, but it will come at a cost (reliability) unless the person you buy it from has taken care of the car and you continue to do so.
Mind you some of this isn't fact but my opinion so take it as you would like on how the generations go.