Clutch locking up

First, I got an oil change last week and also had my differential fluid changed.

This week when Im trying to go into 2nd to turn, or go into neutral to slow down and stop, and basically when Im trying to downshift, my clutch pedal is really stiff and I cant depress it to go into neutral till I force the shiftknob into neutral.

Could the differential fluid have anything to do with this as far as pertaining to the transmission? Any help is cool. Thanks.

No, the diff fluid has nothing to do with it. Its probably a frozen master or slave cylinder. It can also be the clutch pedal assembly binding up, or a kinked clutch line, maybe the throw out bearing collar is getting stuck on the tranny. I cant tell you what it is without looking at it though. Hope this helps.