opinions on mechanics

I was wondering if it would be a good idea to find a local mechanic to take the LLY to. I think the dealer is a ripoff and am not totally convinced that they have diesel techs that know what they are doing. If an independent mechanic is a good idea how do I know that they are qualified? is there some good questions to ask to make sure they are farmilliar with the allison and duramax? Or do I keep going to the dealer??

Thanks