Merlin charged me $300.25 for the rear bumper cover back in April. The tailgate cover is at least $297.99, according to the parts list posted elsewhere on this site. You can probably have a good auto body shop straighten your rear bumper support for not too much. Mine was pretty tweaked and came together without too much difficulty.
One thing to beware of, if you are doing this yourself, is that there are two screws on both sides of the bumper cover that mount ~underneath~ the side cladding. So you have to remove enough screws on the side cladding and drill out the blind rivets in the fender to give you access to those bumper screws.
As far as the frame damage goes, I'd be very very surprised if you got frame damage from that. Mine was salvaged, and appeared to have been hit from both behind and in the front at around 30 mph (Which means was that it was either stolen, 'tipped' by a police car, and went through a fence, or it went through a fence after losing control and jacknifing with a trailer it was hauling). No frame damage at all, tho it did need an alignment. And Commando's Proton hit a deer at 70 mph, tore up the fender and the whole left side, but no frame damage there, either. The frames on these cars are really solid, it's not like some namby-pamby unibody.
Re: The check engine light: The gas tank is right there behind the rear bumper support. The smack might have pinched or jarred a fuel line or caused other problems with your fuel delivery that could have caused the check engine light to come on.
VX: What your Murano dreams it could be...