Have a 2004 Chevy Impala. It is saying it has 3 codes being delected, P1811 = Maximum Adapt And Long Shift P?

have a 2004 Chevcy Impala. It is saying it has 3 codes being delected, P1811 = Maximum Adapt And Long Shift P0128 = Coolant Thermostat P0300 Engine Misfire Detected. I think only once has it overheated over the middle line. and It need to get water in it more often than before. They also said they think... coolant might be leaking water into the engine... I'm not sure if these codes would be related or what could be going on. I have noticed also sometime besideds the engine light being on, the car throdles when warming up. they said they smelled coolant in the engine. Please help? Thanks.