Stick with the grip the Pro has taught you. It is a pain getting used to it, but will be well worth it when you do. It's all about muscle memory. Once you've been practising for a while, it will feel natural again.
I've been told I need to sort out my weight shift as everything is coming from my shoulders at the moment and that's most of the reason I am fading the ball. Also I tend to open my shoulders a little at address.
It feels pretty weird, and almost as if I am off balance, but I know if I stick at it, the results will come. I smashed a few drives yesterday about 40-50yds farther and straighter than ever, and there's no doubt it was because I shifted the weight correctly.