guys there are usually 2 balls at either end of the linkage.
These 2 bushes usually tend to "disappear" after a certain amount of time, lift up the gear cover and you should see a white one around the bottom of the gear selector rod, and then look in the engine bay where you can see the rods again, there should be another golf ball sized one on the other end of the same rod, if either one is missing it would explain the difficulty of getting it into first.
I had the same problem on my mk2.