Yeah dont feel embarrassed,I think we've solved that problem on here (tripped fuel pump switch) loads of times so you won't be the last!!!
It's easy to do on them as well from memory,think its up by the top right by the battery but you were right to he suspicious of the garage as it does seem a bit coincidental it failed while there!!!
Usually on those codes "circuit" means the wiring related to it ie blown fuse,tripped switch,broken wire,blown component etc.
They can be a bit vaugue!!!