If you are not mechanically inclined, why are you telling the lbs your opinion on the problem? That is like me going to my doctor and telling him I am having stomach pains and I think it is an ulcer, do the operation and fix it!
I have no idea what the problem is, all I know is the symptoms. Tell your lbs your symptoms, let them diagnose the problem and quote a price. Why care if you get "hosed". If the price they quote fixes the problem and you will be happy with the problem gone for that price, then great. Don't think about if you are paying too much for a part and so many hours, think of it as for x amount, my problem will be gone.