300 degrees for about 10 minutes with the heat off
then pry on the edges till it breaks loose, you only get about 1 or 2 minutes to pry before they need to go back in the oven, once you get them apart like wayne said you need to put the lense and backing plate back in the oven to loosen the glue to remove it.
Then when you get it apart you need to take the chrome part out of the backing plate there are some screws that hold it to the lens. The bad thing on the 2011+ is you have to tape off the reflector side because it doesnt just come apart like the lower part of the lamp. the reflector is a bit of a pain to get off too, be carefull not to break the tabs off.
then scuff the chrome the best you can, use bull dog on the lense, primer, and then paint. let dry and silicone the thing back together, let sit overnight if possible and then reinstall.