Only your left foot? Was it raining? If it was raining, you should have a wet lap, wet knees and TWO wet feet.
On a more serious note, if you think that this is brake fluid, keep a very close eye on it. If it's noticeably masking your foot wet, it's leaking pretty good -- and soon, your brakes (or clutch) will fail. It will also be eating up all the paint underneath the master cylinder.
It's impossible for me to tell you whether a rebuild kit is all you need without looking at the cylinder bore. You will have to do that and make that decision.