I just changed mine, as it was hard to get into gear at times, especially at a dead stop into first gear when cold. It was quite notchy, or resistant, in all gears. I used Mobil 1 ATF + 2 oz. Ford Friction Modifier Additive (Primarily used for LSD's). My car shifts sooo much more easily now. Like buttah, as I told my wife.

It really is easier than changing the oil. Find the How-to in the FAQ's. HTH.
Edit: Just thought of something: does it help the car go into gear if you pump the clutch pedal a few times first? If so, then you probably have a problem with the hydraulics of the clutch (Master, Slave Cylinder).