So this isn't the first time I've encountered this problem, but I still am not certain this time what could fix it.

Long story short, I have a rear caliper that is sticking and I'm getting that oh-so-awful whooshing, scraping sound. I've had this problem with a Buick Skylark I used to own, which cost me $300ish to get the whole front brake system redone (rebuilt calipers, new rotor), but this one doesn't seem as bad. It's not nearly as loud and the brakes seem to grab just fine.

Now I just had my Crossfire in for my spoiler problem (that seems will never be fixed) and the dealer I took it to did one of those free multi-point inspections. I know most of the time, they'll put something on there you don't actually need so they can get more business, but this one actually brought up some pertinent info. 3 things, brake fluid contaminated (recommended replacement after 2 years or 24,000 miles- I just passed 24,000 and am coming up on 2 years), throttle body is dirty, and they recommended that nitrogen tire fill (which is a nice thing, but gas stations don't carry nitrogen if I need to adjust tire pressure, and no way in hell am I keeping some stored around my house).

So my question is (along with any advice/fixes you can give me), if I get a brake system flush, and if necessary, have the rotor put on a lathe, will I be good? Will doing the brake system flush possibly solve the problem by itself? It doesn't seem to be as bad to were the rotor would be warped from heat, but it definitely needs attention to either fix or prevent the problem.