Hi, I just spent a week in Paris. At the health food store I went to, there were many gluten free products that were German and a few that were French. Schar brand from Germany was very popular and they had a wide range of products. Check out their website; it shows lots of items. If you can't find them in Grenoble, it might be a good excuse to make a regular trip to Germany (or Paris) to stock up. ;-)
They have clear labeling on foods, usually in many languages, so I was able to easily shop at the grocery stores.
Dining out was relatively simple in Paris - they tend to make reduction sauces for meats that don't have added flour for thickening. As long as I chose a restaurant that served some type of roasted or grilled meat, after consulting with the waiter and/or chef, I was always able to find something I could eat. My French isn't the greatest, so I would usually ask (in French) if there was someone who was fluent in English who could take my order. One time I had to stumble through the whole order in French and try to explain my gluten issues - it worked out just fine.
Enjoy your time in Europe!