2000 Jeep Cherokee Electric fan

My Jeep was a recall in November of 2007 to replace what might be a defective cooling fan. When the temperature in South Carolina started warming up I noticed my engine getting hot in town but not on the hiway. I checked and found the fan would not start after engine heated. I took it back to the dealership and cpmplained that it worked fine till they replaced the fan. They checked and said it was a relay and they were not responsible for it. They wanted $250.00 to repair it. Where is the relay located and does it take a mechanic to replace it?