I'm having an intermittent problem of loss of clutch disengagement. I believe the slave isn't moving enough to disengage the clutch. But the slave cylinder isn't leaking so I figure its the master. My question is hard is the master cylinder to replace

 

We just replaced the slave today on my 05 Scion TC. Started to engage again... when I got to a light, nothing. I can't get into any gears at some point. I attempt first gear, and the entire vehicle wants to shift forward with no gear engaged.

When replacing the Slave . We measured the piston moved about a half inch on the old one and we got the same on the new. Our next intention is to replace the Master Cylinder.
No leaks anywhere either.

Anyone else have any suggestions. I am reading all over these forums, but I do not see the end results for others. The master cylinder doesn't appear to be too hard to replace and we priced it locally around 28 bucks.