Gems are cheap mate, £20 will get you one and you need 30 seconds to reprogram it

The issue comes when you get a gem with the wrong numbers on it

It's up by the drivers side above the accelerator pedal and you have to unplug it a certain way as well before you remove it

If you ask over on talkford.com for a guy called Alex of lxxy I think his user name is, he will probably be your best bet
There are plenty of write uos there too if you can navigate your way around the wiki page