First thing we need to know is what is the voltage of the battery.
If it isn't at least 11.3V, then the solenoid may not want to engage.
Did the mechanic check power to ALL fuses?
It is quite possible that in all the attemtps to start the vehicle, a fusible link has been blown.
These all need to be checked.
I have to ask though, if you have your mechanic, why don't you use him to change your oil, instead of where you went?