Swapping the hubs should be easy enough. Don't listen to the FUD about re-using spokes; just inspect them for damage. And you don't need a wheel stand to build wheels; I can get a front quite close to true just by doing up the nipples till the threads just disappear (careful of sleeved rim joints), then just adding equal tension around the wheel. I just put it in the bike to finish it off, using the brakes as guides, flip the wheel to establish dish. The rear's different only in that I put it in the frame earlier to check roundness before I really crank up those DS spokes.

As for mixing HG cogs, it's about the fact that a 17 from a 28-25-22-19-17-15-13 is designed to sit between a 19 and a 15, and is a different animal to a 17 from a 32-28-24-20-17-15-13. HG cogs don't play nice where they don't belong; all those fancy cutouts and chamfers allow the chain to ride lower over the cogs during a shift, eliminating the chain jump from the higher chain falling into place as the shift completes. When you mess with the HG program, that old jump comes back.