You are sure about the intonation? I have bought Warmoth 24 3/4 "conversion necks" and I think there could be issues just putting a regular short scale neck on the guitar and being able to intonate it.
Warmoth sells the conversion necks for strats. That is what I bought for my strat. You may want to call them and see if they will share the trickery.
As far as getting a luthier to grind the sides and a narrower nut etc. I have a luthier that can do that so fast and precise it is crazy. He would have your neck done in 1-2 hours. If you get a short scale neck you will still need to have it set up, frets dressed, nut filed or replaced etc. It is never bolt it on and go. It will need the skills of a luthier. Warmoth will make you think it is that way when you buy the neck, but when you get it and then phone them they point out a page in the bowels of their site that says it will need professional work.