Gumbo Advice

Some friends are coming over tomorrow and I am going to try to make gumbo for the first time.

I'm going to use this recipe from the Gumbopages website:

http://www.gumbopages.com/food/soups/chixsaus-gumbo.html

I think what I will probably do different is to first cook the chicken in water with vegetables to make a stock early AM, take the meat off, and continue to cook bones for added richness until 4 or 5. Then strain the stock and use it for the gumbo.

At that point I will start the roux and gumbo proper as per the instructions above.

File is supposed to go in at the very end off the heat, correct?

Any one have advice or other hints?