Transmission/Brake Problems?

This past weekend my Accent 2002 started driving a little weird. It's hard to explain, but whenever I'm not putting the gas pedal down, there is a slightly quicker rate of slowing down. Also, the gears are shifting very clumsily and heavily. I'm worried that either I'm having transmission problems, or I have a stuck brake somewhere. Does anybody know what this/how to fix it?
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fluid hasn't been changed for at least 4 or 5 years. I'm taking it in on Friday to get drained and filled. I was just wondering if this was an indicator of a bigger problem, or just the fluid.