Lee,
If you are an American Citizen and you've lived at the same address for any length of time, it should be fairly simple. You have to pay for the item with a credit card and once you win you need to be sure to give them a good address. The address must be a known street address (no post office boxes) and hope you have a good home phone number (no cell phone) when completing the EUC. If you don't have a street address where you get mail at OR (not and) you don't have a home phone, you maybe asking for trouble. I'd contact the Defense Logistics Agency folks to see what you can do to mitigate the chances of not getting an approved EUC.
SF97, ensure the everything is correct and matches the frame number and date of manufacturer. If not send it back until it is correct. As with anything, sometimes you win, sometimes you loose. If things get weird you can pop on and ask.