I've removed and replaced the standard grips when I fitted heating elements underneath and whilst it's not the toughest job in the world I wouldn't be in a massive hurry to do it again.
The heated grips would be a different matter all together I would imagine as the chances of breaking an element could be quite high. Having said that they got em on in the first place so the replacing bit can't be that hard. It's the removing you need to worry about
I'd have a chat with who ever put them on at the dealer first as depending on the glue there may well be an easy way with the right spray/solvent etc. At £300+ they're expensive to f**k up.