Highlights to One color? Help!

My hair is noramlly really dark, but for the past three years I have been getting Blond highlights in. I was going to the same girl and she would do lots of thin highlights, so my hair looked blond, you could't really see the dark hair at all.  She usually bleached the roots, and used toner.

6 months ago she moved and I got another girl at the salon and she redid my roots, but she did them wrong. She had two different shades of blond, neither matching the blond I already had, and they were more "chunky" high lights. Since I was getting it done in three months anyway, and it didn't look too bad, I didn't re- do it. Well now my roots have grown out and it's time to get it done again, but this time I am thinking dying it instead of highlights. It's not the same color anymore anyway.

 

Would this be hard to do? Also, my hair is really healthy, but I know with a lot of bleaching you can have chemical breakage- do you think this would make it over processed?

 

I want to get my hair done next week, so any suggestions or comments would be great!