I don't recommend anybody take on this kind of job, but here's a pictorial of how to get 'er done.
After pulling out the old frets, the fretboard has to be planed out level again. If the neck is badly warped, this poses challenges. This particular guitar couldn't simply be treated with heat and pressing. To plane the neck properly the neck must be supported. I used a sandbag for this guitar, being a neck-thru model and very flexible, it worked well. I plane out the fretboard with the proper radius block/bar. Work out the warped areas until level again. I warned the customer that we would need to take off a lot of material to get this neck into the playing realm again, it was extremely warped/twisted. On top of that, it had a compound radius fretboard which starts at 10" and progresses to 14", so I have to check my work constatly. After sanding it level using a coarse grit, I work up to finer and finer grits until polished. Then it's time for new frets.
Clean out all the fret slots as well as possible. If the fret tang and slot size is compatible, hammering them in should be an easy process. This one wasn't. Required extensive cleaning and fret tang size was slightly too wide. If you install frets with wider tangs than fret slots you will likely compress the neck into a back bow. Not a good idea. Widen the slots.
After taking off all that wood, the nut shelf had to be lowered. I used the radius block (with a router) since it was easiest to make level resting on the fretboard. Take off small increments at time until the nut sits just right.
Once the frets are in place, trim off the excess, dress the ends and give it a final level, crown and polish.