I'm a bit confused by this. Did your engine overheat, or did your fuel pump overheat? I'm perplexed by a fuel pump being damaged by engine overheating. What operations does your invoice state were performed? If the coolant was really low, the system may have sucked air into it and there has been air entrapment inside the system that is working its way out. Was this service performed by a dealer or by an independent mechanic? I'm not sure about the key getting hot, but I'd be worried about it if it continues. What's your warranty status, i.e. year and mileage?