Haven't seen many conversions on UFO's around the forums, so probably a long shot that someone has done it. It should be the usual power driver and LED emitter array type setup so I would think it should be possible. The big question would be why it stopped working. If the driver(s) burned out, then no real point in trying to convert. Usually the reason folks convert a light is because the driver is a singularly large expense in a DIY build, so using one that's on hand in an existing light is a huge savings. The heat sinks are typically sized for the wattage output of the drivers in the light, so more saving in being about to re-use them, but heat sinks don't really burn out so likely not the reason why it's not currently working.
Really you're probably just going to have to bust out the screwdrivers, pop it open and see what type of components you've got to work with. Take some shots of what's in it, in particular of any labels on the driver(s) and post them up and someone should be able to help you figure out what, if any, type of COB's would be a good match.