The whole gearnob itself is actually glued on and is moulded onto the gear stick, which is a really firm and strong grip. In order to actually remove the nob then you will need to saw it off as the whole unit itself is not bolted onto the stick.
I used a small hack saw and had to cut 3 areas of the nob to start with, then when I made it looser I actually just got a long flat ended screw driver and drove it up the nob and it popped off - that takes about half hour or so.
For the white 'skeleton' under the nob you will need to saw it off with the same hack saw in the same 3 areas of the nob, which is just either side and the top centre of the white nob. That is the hardest bit of the nob and you have to keep persisting until it becomes looser. Once its loose then again just prize it off with a flat ended screwdriver. That took me just over an hour to do and I was sweating like a pig.
You will also need to just skim off the bits of white crap that are still stuck onto the gear stick and rub it down with some corse sand paper for about 5 mins to make it a nice smooth fit for you new one.
Doug