What ever your situation is, tell him your not happy with your current mechanic or you are new to the area and are looking for a new place to start bringing your business to. I have seen this work many times over and over again. . Store managers are always under pressure to get their sales up. One shop I worked for was told to give at least 20% off repair services just to get the business up!
Ask what kind of warranty will come with your parts and services. And always ask to see your old parts! Bringing in coupons from other repair shops is another good idea. Ask if they can meet or beat this price. With the coupon in hand they will most likely do it. Happy Driving!