Subaru Legacy L 2.5L

I recently was driving my Subaru Legacy and it
broke down and when I pressed the gas nothing
happened, the check engine light was on before I
broke down I ran a diagnostic for the check engine
light and the error code P0118 came up or “Engine
Coolant Temperature Circuit High Input
then before the car stopped working the At oil temp
light came on. I read after that this was a result of
tranny fluid overheating which could be from low
tranny fluid since we just replaced the headgaskets
we didn’t add more tranny fluid would this cause
my gas to not function and is it from the low tranny
fluid?