To may also lose some other features with the later Gem. The wipers, and hazard light switch can be affected. Not all Gems have three blinks - I think the lower spec models did without it.

Your best bet is to fit it and see how it goes. You can always swap back if it doesn't work. I've heard that you can have the Gem reprogrammed if you do lose functions, but I've no first hand experience that's it's true.

As far as I know the Gem is dependant on the model spec, not the engine, so you can swap them between fuel types.

I also recall that there is a sequence when you install it, so the main power connection goes on last. But I can't remember which one it was. Maybe ask on Talkford, as there will be people on there who will have done it.