Be careful if they say they can lighten dark hair to pale blonde without bleach. Some lighteners use ammonia, or chemicals that are similar to bleach. If they tell you there will be no damage, be VERY careful. It doesn't matter if you have very healthy hair; it can still be damaged. If they are careful in the timing process you should be fine.
Foiling is time-consuming and expensive, but it is the best way to color long hair, especially if you are getting more than one color. You definitely don't want to mess with a cap if you have long hair.
If you sometimes wear your hair up, make sure they put some highlights underneath, at the hairline.
Are you getting blended weaves or bold chunks?
Highlights are very popular now, and I'm sure you will look great! :P
Please post a photo after.