No kit experience, but a FR isn't that bad to sort out. Slightly more fiddly than a Strat trem, but if you ignore the locking aspect, the principle is just the same. You just need to keep the baseplate flat when setting things up before you get the spring tension correct, which is best done if you make some little wooden wedges to keep the trem block in position.
The kit's headstock is angled, so no need for a string bar on the headstock.
Thanks Simon, did a bit of research etc on the FR, not to scary, will give it a go, kit looks fairly straight forward. This one is for my son, he always wanted a 7 string. I will reclaim the SG I originally built and rework it and tidy it up - was never really happy with the finish so solid colour it is for that one.