I have swapped mine over. It's fairly straightforward however when you get to the area around the exhaust tips on the left hand side it's really easy to bend and crease the diffuser in that area as there isn't much rigidity to enable you to give it enough of a pull to get the tabs out. My advice is soak the s*** out of it in WD40 in the area between the bumper and the diffuser, all away along there is like 50 plastic tabs in there get in the crease line between the two and spray the lubricant in there. Would also be better if the diffuser was cold rather than having been sat in the sun as it will make it stiffer and easier to pull off without bending and creasing. Just have to be patient and be careful with the far edges that tuck in under the bumper too .
Obviously you can take out the mesh section too when getting it painted. The two pieces come apart.
I was replacing mine as it had some marks on it so didn't care too much if I bent it but I did indeed end up creasing mine near the exhaust tips. I got my new one from the parts ordering section of this site, pretty sure it was around 80ish quid. Might be worth getting a new one and spraying that as there is a good chance you will destroy your current one getting it off