Thank you for the answer!
If my situation was a bit different, I would probably do just that--go to a professional. However, I live in a fairly small town where the few surviving hair salons feel no need to price competitively. It's ridiculous, but nearly everywhere you go in this town will charge you a minimum of 100 dollars for touch-up work that doesn't involve bleach. I can't really afford that.
There is always the option of driving a couple of hours to get to the nearest, larger city... I guess I'm just a little apprehensive about doing so.