Sling Media doesn't have an outside repair team, but If you are looking for a fix, I would try and see if there are any local technicians who are familiar with the Slingbox. You also have the option to do an out of warranty replacement purchase through Sling or of course, the upgrade program, which would give you a discount on a new Slingbox. Depending on what may be wrong with the hardware, an upgrade might be more cost effective. I've linked the upgrade program page below, just in case:
I hope this helps!!