You can try www.fitday.com to help you with tracking your carb intake during the day.
Pop is a YMMV (your mileage may vary) sort of thing. Dr. Atkins does warn to avoid Aspartame, but there are diet pops out there that use Splenda instead like Diet Rite and Diet Stewarts. It's still best to drink mostly water, though, so try to limit your diet pops to 1 a day for now. Herbal iced teas often make a nice change of pace, too. HTH