The answer is maybe it can be fixed. I had an earlier SLK with the same problem but it had halogen headlights. The prior owner told me the dealer told him they had to replace the entire assembly quoted at $700. I looked at the EPC online and saw the gasket is available for about $15. I ordered it, removed the assembly and replaced the rubber gasket...no more leaks. The entire job took me well under an hour, and I work slow.
The first thing you need to do is verify that for your car and HID headlights the assembly is re-sealable...some are and some are not. You can inquire at the dealer's parts counter or look here after setting up a free account:
http://epc.startekinfo.com/epc/