Since the person at the camera shop would not explain what he did, it is likely that they did not know what they did.
It is possible that the camera has a reset button or reset proceedure. Some cameras do have a reset button. Since Nikon does not publish an online user's manual, I can not tell if it does or does not.
Check your user's manual and see if you can find any mention of a reset.
While I was on the Nikon site I noticed that there have been several Firmware updates for that camera.
I suggest you get the latest update (firmware 1.8) and update your firmware.
Click on Firware Updates
In the Search Text window - type in - 5000
Then click the Search Button.
You will see 1.8 updates - choose Windows or Macintosh.
have had a nikon coolpix for several years and generally happy. after last download (CF card taken out, emptied and replaced), it had battery image top left and C.R top right. nothing else and no repsonse to inputs. if put in mode to view images it was fine, whether card had images on or not. could zoom on image and scroll image.
changed battery, card etc but no effect. played with sttings and somehow chganged it to C.3. but couldnt reverse of move it from there.
wife took it to camera shop and assistant first said needs new mother board, but when asked if it was a settings problem, played a while and got it back to normal. didnt charge but no interest in explaining what had been done.
OK but what if happens again. does anyone know what was happening and how to deal with it