Yes, you need to fill out the VAT form. When you make your purchases from the store in Paris, the SA will automatically give you the form with everything filled out for you since all they do is stick the form in the register and it prints the totals and stuff on it. However, remember to request it as well, as some may forget. That is very slim though since they do it every day all the time since alot of purchases are by tourists! This applies to stores like Sephora and clothing stores, not just handbag places.
Anyways, make sure you get to the airport in plenty of time before you leave Paris so you can drop it off at the VAT counter of your airline. Then your refund to your credit card should come in a month or two.
I never had to show my purchases at the counter, but some people at the counter may make you.
Bon voyage!