Stupid human tricks: weekend edition

In order to install a front rack and basket, I moved my front hub light. That actually worked out as I specifically bought a rack with a light attachment space. The stupid human part was partially cutting the wire to the rear light . Amazingly the light still...partially worked. Due to the front light move, the rear wire had to accommodate the move also. Now it was very loose when turning to the right but taut turning left. So taut it snapped. Double

Since I know nothing of electronics, I'm going to have to take this to the LBS. I imagine the materials cost will be negligible but am unsure how labor intensive this will be? Is it a case of patching the wire where it snapped? Or will the mechanic have to strip the wire all the way back to the rear light? The wiring is tucked inside the bike, runs along the fender and there's a rack there too.

I am also assuming this is something any old LBS can take care of. Or it a more niche skill that not every LBS has and I will have to look for a specialist?

I really liked the rear light--where the front light is pretty weak, the rear is large and bright.