the jdm itr headlights should already be painted black. did you get one itr and one sir-g? the sir-g ones are chrome.
anywho, to bake them you want to remove all of the plastic stuff on the back of them (obviously they'd melt or catch fire). then you have to preheat the oven at 400 degrees. some people have used as little as 275 degrees. bake them on a tray with tin foil over it for about 3-5 minutes. shut the oven off, and let them sit in there for a couple of minutes. when the seal has melted, you should be able to move the glass around by hand WITH GLOVES!!!
when you've got them painted, just seal them back up with clear silicone. you can get that pretty much anywhere (hardware store, walmart, auto supply stores...).