Just a note, I always take them off, because I personaly think they are butt ugly. I always keep the rear adjusted and I'm very careful not to ever knock the bike around. (I do leave them on on the wife's bike though) So far knock on wood in 50 years of riding bicycles I have never had a chain suck and take out any of my spokes.
If your LBS can't do this simple of task I would never go back to them for anything, EVER!