Hi Neon.
I dont know what year your bike is but I have an 04 Rev3. I think they are all extremely similar (not sure about 07) I have changed the original lever and new ones quite a few times (05-06 levers are longer on both sides of the pivot). To remove the lever you pull it backwards. To replace them I have to take a screw out of the bottom of the plastic guide to let it move sideways a bit, the chain stays on. I think someone mentioned breaking teh plastic?, That may be a different guide then.
If you have REALLY badly bent the lever, then that may be a problem, otherwise once you have all the bolt, nut, and pedal bit off Get on the left hand side of the bike, lean accross on the rear subframe pull on the swingarm to compress the rear suspension, then wiggle the lever back and up. pay attention when it comes out, getting it back in is trickier!.
Good luck.