WWWAAAAAAAAAHHHHHHH!!!!!!!
That's right!
Don't use anything during tracking unless desperately necessary, specially with acoustic instruments. Whatever you use now, you'll have to live with it, or track it again...if the one you already recorded wasn't the best performance of your life.
I learned it the hard way.
The M-S is the mic config I like the most, specially for classical guitars. The sound is lovely, neat, sweet...
Our buddies here already taught you how to do it, but for Dragon's sake, don't compress it before!
Peace...
PC