Heat fan blowing cool air out. Changed thermostat & now overheating bad.

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Took it to Jr @ Ray's Auto Repair in goldsboro nc. He changed thermostat again & said it needed a new waterpump to stop overheating & needed to blow the air though the inlet of the heatercore to unclog it. We picked the car up & the same mechanic JR @ Ray's said don't worry if you smell antifreeze until it burns off of motor because it blew all over from heatercore .15 miles away , the engine light came on & stayed on & it runs like a 3 legged dog! Misfiring ! 5 of those miles were from Ray's Auto to our home , & this was around the holidays so we didn't drive the car until 5 days later & he wanted to charge another 500.00 for something i am so scared they Jr. Messed up !!!! PLZ Help !! We barely have enough money from S.S.I to make it each month.What is your opinion ?Thank you & GOD BLESS