I built a lap steel over summer '06 with my father. You are definitely saving yourself a lot of work (especially with a non-lap guitar) by buying a prebuilt neck, although the precision work for measuring and sawing the frets can be enjoyable. The Stewart-Mac fret mitre box and saw worked a charm. I don't like how the pearl inlays came out on mine though, might drill them out and replace them in the future.
The electronics can be tricky, especially if you are like me and not too good with a soldering iron. My lap steel is very quiet (compared to other guitars in the same amp) and I suspect it is leaking signal to ground, although it sounds OK. Another thing to redo in the future.
You didn't mention what you are doing for a nut. I had a little trouble with this on my lap.
pictures of my lap steel at: