Heater and gas guage

Recently, my car stopped working on a highway and the repair station that I brought the car into diagnosed at first that it was two sensors, which they replaced. The car still didn't work and then they diagnosed that the fuel pump needed to be changed. When I picked up the car, my gas guage was not working and the adjustable fan/blower inside the car did not blow any heat through the vents when I adjusted the fan from low to high.

The mechanic insists that no heat is supposed to blow through the fan which is not the case as it was working properly when I brought the car in.

Can it be that they did not reconnect the heat properly when they replaced the sensors; also, can you advise what the problem might be with the gas guage?

Thank you.