I always hear bad things about home highlight kits. All over color is easy but highlighting is not as easy. I did it to myself years ago and it came out fine but I only did a few highlights in the front just to add a little something. I don't think I could have done my whole head.
If price is the issue, and you don't trust yourself to do a good job you can always check a Bo Rics or Fantastic Sams or something of the like. Their prices are very low. Most people would gasp at what I just typed stating that it's a class B salon and the stylists must not be good.
I worked at a class A salon as a receptionist for a number of years and walked out of there with plenty of bad haircuts and questionable dye jobs.
It all depends on the stylist, whether they do it the basement or the fanciest salon in the world.