Archivo General de la Nacion Mexico and familysearch.org

I have records/data from the Archivo General de la Nacion (Valparaiso, Sombrerete, Zacatecas, etc) which I find very helpful. My records were extracted from the Archives themselves and sent to me by a friend. Unfortunately I have had little luck in trying to find out how to locate and use the Archivo General de la Nacion; their website is not user friendly and so far useless for me. I emailed the Family History Center that I use and asked how to use the Archive General de la Nacion, and I obtained the following response, which I will use in my investigations of the Archivo General:

"I did find quite a few listings in the library cataloge. Go to www.familysearch.org . Then click on the Library tab, then the cataloge tab. Then do a keyword search for "archivo general de la nacion". Some of the entries are on microfilm. Some are not but if the ones that are not are of interest to you, you can order a copy of an index for that item for the name of interest. I can show you the form later."

Ed