They should make Floyd trems for all major nut widths. You probably wouldn't have to use a router unless the trem cavity is too small to fit your Floyd. At worst you'd probably have to widen it a bit, at best it would just fit.
Lots of guitars, especially in the 80s, had Floyds without a recessed trem cavity. I've seen guys put Floyds on standard trem guitars without too much hassle.
If you don't have to use the router for the body, the most difficult part of the process will be trimming the nut area properly. If I remember correctly, you'll not only have to shave off what material is there from the nut forward, you'll probably have to make the cut deeper as well. Check your truss rod adjustment (if it's at the headstock) to make sure that you have room to put in a taller nut if you had to.
Then I guess you'd have to properly measure where to locate the bridge studs and make sure you install it really well. I'm not familiar with the differences between standard trem routing and floyd routing, but just make sure where the studs go have a lot of material underneath and that it isn't too close to the routing underneath.
As for springs, they've all been the same to me over the years. I've put the same trem springs in old Fenders that I've put in my ESP. Some are longer, some are thicker, but a spring is a spring. It will probably come with the spring claw and springs too. You shouldn't have to change the claw either. Then you'd probably have to deal with re-soldering the ground wire(they're usually attached to the spring claw).
It will probably come with some instructions too.
