2003 Cadillac Deville LED brakelights

I tried to change my brake light today and discovered it was what I believe is an LED system. I went to a local parts store prior to disassembly of the brake light and they sold me a bulb brake light. I called around and each parts srore said that for that year model, a bulb is what is showing up as the replacement part. I had a 2000 Deville prior to this one and had no problem changing the lights. If this an LED system, can I convert it to a bulb system? With an LED system, what part do I need to change out (ie...the entire assembly)? Is there a less expensive alternative to going to the dealer for this part?
Thanks,
Nick Soto