Hey mate, if your FGX has the original gearbox, it'll be a TR6060.
My advice would be to choose your workshop and tuner first. They will tell you what you need, and what they like working with.
I sometimes feel for workshops and tuners who have people coming to them with unknown parts and workmanship, and expecting great results. It's often cheaper to get it all done together, in house.
If you're going to modify and tune, do it properly the first time. Get valve springs done. You don't need head studs.
I think just for tune anywhere from $1000-$1500 seems to be the going rate.
Consider getting a new clutch, and tip to bottom service at the same time.
Hope that helps