yep very easy mate.
basically:
1) pull up the booting around the gear stick, (becarefull nto to break the plastic tabs!!
2) look under the plastic cover and on the inside you will see a rubber boot held in place via these plastic tabs.
3) pull the top cover boot up (leaving the rubber boot down)
4) you should then see a copper ring around the bottom of the gear stick, pull this off with a pair of plyers, (you probably will need a new ring so order one in)
5) once that is removed, slowly twist and pull the gear stick off
oh btw i have a red momo gear knob if you want it for 15 delivered
oh, aftermarket gearknobs should either fit on like standard gear knob or should have some grub screws that you can screw in to the gear stick to hold it still.
hope that helps
Adam