Brake booster got replaced now having issues that weren’t there before

I would return to the dealership to have the repairs rechecked for proper completion. The loss of power could be vacuum related (which would be booster related), and the lights staying on could be brake pedal position related. Of course, these concerns could be related to other problems too, but it would seem reasonable to question the work performed as these concerns appear to be new following the work, and both could have correlations to the work done.