You are on the right track! It is great having a running store that you can go to. I had one in my old town and loved it when they fitted me for shoes. I usually wear a size 8.5 and they sold me a size 10!! I never would have thought that my feet would need that much room but the shoes have worked wonders.
Don't expect all of your aches/pains to go away tomorrow when you wear the new shoes. Your body needs to adapt to them a little. Give them a couple of tries before you make a decision about them.
Oh, and your race times are fantastic. Try not to compare your times to other people (I know, it is hard...I still do it too). Compare your times and how you feel at the end of the race to how you did last time on a similar distance. My finish times haven't changed all that much but I now feel energized and bouncy when I finish a 5K, as compared to the huffing/puffing/dying version of myself that used to be bending over at the finish.