not too hard at all. You need the S subframe rails, undertail, cheese grater/piece the tail light bolts to, and a seat.
There's space for everything under the seat, plus you'll have a little extra room since your ECM and fuses are in your front fairing. You'll have to make a new bracket for your rear brake reservoir.
I think that's all there is to it. Plenty here have done it though, so I'm sure someone will know if I missed something.