You may have a problem with the coolant level sensor as that should have flashed up first before it went to 120 on the gauge .
It Could be a sensor fault for the engine temp .
It could also have dumped all its coolant in one go and it was actually that hot .
Youll soon find out though as over heating may well do the headgaskets , well the garage working on it will and im guessing they will have to fix it .
My guess though is it will be fine once the leak has been fixed .
Thats my 2 pennys anyways .
It Could be a sensor fault for the engine temp .
It could also have dumped all its coolant in one go and it was actually that hot .
Youll soon find out though as over heating may well do the headgaskets , well the garage working on it will and im guessing they will have to fix it .
My guess though is it will be fine once the leak has been fixed .
Thats my 2 pennys anyways .