Radio theft system

Hello, I am having issues with the stock radio in my car. At first the display was coming on and off but the radio was still working. Eventually the display quit working entirely. Now the radio does not work at all and also I came out a few mornings to a drained battery after the car was not driven for two days in a row. I replaced the battery with a new one and life was good until recently I am having drained battery problems if I leave the car sit for over twenty four hours without starting and running/driving. So I am guessing the radio is my draw and needs to be replaced. Well I called a few junkyards and asked about a used stock radio but now my concern is that I buy and install the radio and it locks and will not let me start the car due to the theft system. I gave the junkyard my VIN number and they said I have a U1C coded radio and I found that code on an 2006 Saturn ion radio and everything I have seen on the net said they were interchangeable, but again concerned about the theft system and having to have it towed to the dealership and end up costing me a bunch of dollars. Any idea about the theft system when swapping out the radio?