Personally, I might be inclined to take another approach.

I would look up the bike manufacturer's web site, locate their 'contact us' link, and fire off an inquiry to them, concerning what your shop said. Ask the company if that is actually true, or if it is a training issue for the shop's mechanics. I am betting that the company will say that it is a training issue, and (ideally) that they will have their sales rep contact the shop and arrange additional hands on training. Either that or the company will pull out of the shop in the not too distant future.