how long is it going to take from start to finish est.?

You have to have a place of business, zoned for it.  DON'T try to do it out of your house.  In theory, you can do it out of your house, but it's less likely to be approved.  

You have to have a business license.

Order the application for the FFL off the BATFE website.  You can print the docs, but why?  They are free and come in the mail in under a week.

Fill out the application and send it in.  

Wait.

Did I miss anything?

Quoted: Did I miss anything?

That is a pretty good reply. However, as one who used to have an FFL several years ago, it can be a PITA as to paperwork, business taxes, etc. You really have to figure out if you are doing this to make money or have fun. Sometimes it can be one or the other and sometimes neither.

You will also have to get a state sales tax number, city and/or county business tax license and if they still have them a state pistol permit (for sales only). All in all, don't expect to get rich.