I just replaced mine. The float is attached to an arm that pivots about a point. The arm then wipes across a variable resister so the resistance changes as the arm and float move. Based on this and the ease that my arm moved, I doubt the float is stuck. It would take a lot to do that.

So the problem with mine is that the resister contact was worn through, specifically at the 3/4 mark. As soon as my tank went down to 3/4, the gauge would act all screwy.

Here's a picture:


The resister is in my right hand and the float is all the way down so that would be empty. I don't think there's an easy way to fix it. Your best bet is to replace it.