It does sound like your slave cylinder if you can see fluid under the bell housing. Sadly, that's where the slave cylinder is located: inside. I'm afraid it's a long and awkward job, consisting of the following bits needing removal:
Driveshafts
Rear prop
Front subframe
IRD
Gearbox
After doing all that you're going to want to not only change the slave cylinder/release bearing, but the clutch plates as well. Get the dual-mass flywheel checked too as that can cause problems with clutch judder. You might want to consider the master cylinder being changed too as they can fail at the same time as the slave (they're both ****ty bits of plastic).
Mine went a few Christmases ago, and it cost over £800 to fix at an independent, which was nice. I didn't need a flywheel though.
Sorry, I guess that's not what you wanted to hear. Some people get away with simply bleeding the clutch to get the pedal working again, but with fluid clearly visible I fear the worst.
Of course, all of this work is feasible at home if you're handy, and you'll save a packet, but you will need to allow at least one full day to do it in. Probably more.
All the best.