First, calm down.
Second,analyze what is wrong.
You have power to the unit.
That is good.
The power goes to the defrost timer and cold control,then to the compressor and condenser fan motor.
You can ohm the cold control to see if it is Good or not.
If no good,jump it out for test only,to see if the compressor and fan motor come on.
If you have power to the compressor start relay and it does not run,ohm the compressor terminals on CSR to see if it is shorted or open.
If the compressor reads OK,replace the start relay.
If no power to the compressor and the cold control is OK or jumped out,suspect a bad defrost timer.
Why was the heater replaced?