i know this is late, but for future referrence, flush your coolant, change termostat and temp. sensor. It will cost you less than $50 for the parts. DONNOT buy your parts from autozone, parts look the same but they blew my intake in less than an hour after replacing them. the Temp. sensor is right in front of the termostat below the throttle body on the right side of the engine. Replace both, and again do not buy your parts from autozone. Also check your fuses in the lower fuse box under the hood, 9/10 times you will need to replace the 25AMP fuse ( it's clear).Your heating problem is Dextron, it clogs up your coolant passage, use regular 50/50 antifreeze instead. After you have fixed your issues, your best bet is to get rid of your impala ASAP.