I would only do "low lift" highlights. Too much bleach and you may wind up with all the lightened strands all over your floor. My only experience with professionall highlights left me with red (and I mean Elmo red) highlights. They were supposed to be chocolate brown. I found out the hard way what color they were:
Me (sitting in court waiting for the judge to come in):
Court Officer: Hey, A-----, nice red highlights! (Smirk).
Me: Wha?
CO: Yeah, you know, your highlights.
Me: (Gets up, RUNS to the bathroom...)
In the bathroom: AAARRRRRGGGGHHHHHHH! RED hair!
I had to go back twice to fix it. THEN they fell out.
So I never highlight. The most I do is cover my grays with semi-perm (28 shampoos) color in one or two shades up from my own.