So over the last 7000 miles or so, my clutch has been slowly failing, meaning I have to push the pedal farther and farther down to disengage the system. There is no problem with the clutch slipping, and it reengages smoothly, totally driveable, but it's not getting any better and I have some money to replace the culprit. It's not losing any fluid either. My first instinct is that it is the master cylinder because that is what provides the power right?

 

I would just replace them both, they're not expensive and the extra time to do the slave is only about 15 minutes. Chances are if you just replace the master the slave will need done in a few months anyway.

 

I recently had the same problem. you need to replace the master, the slave and the line that runs from the firewall to the top of the slave cylinder (metal/rubber combo). The rubber wears over time,a nd can cause a leak. Advance Auto has these for about $18 the slave cylinder is about $15, and the master is about $25. Replacing all three will ensure even pressure and you may as well while your in there.

 

I had a simular issue, so I bought a slave cylinder, and never replaced it- only because bleding clutch line seemed to help. I guess it depends on how soft the pedal is. Mine was just a little softer.