Check if you have fluid on the pedal or an some extra fluid around the clutch drain hole. If you have fluid on the clutch pedal it is your master that is going, if you have more fluid around the drain hole then its your slave, but like you said it is best to switch out both the master and slave. It is a very simple job to do, I thought the hardest part was bleeding the lines.... Did the job over the summer when mine went.
When replacing my master I had troubles getting the box out from the side of the big brake box assembly so I had to unbolt that and shift it a little to the side to slide out the clutch pedal and master assembly.
here are a few good links, first is for the slave, second is for the master.
It really is a pretty easy job