There's lots of good information here:
"I'm pregnant for the first time and think I do want to breastfeed. Help me?"(I realize you're not pg for the first time, but a lot of the advice rings true no matter if it's your first or not.)
Also, the best thing you can do is find yourself some IRL support now -- whether it be a lactation consultant, a LLL group, or a hospital breastfeeding group -- and talk to them about your concerns. Make sure you'll have some help available when the baby comes because when you're dealing with the craziness of a newborn, the last thing you want to do is try to find help. Expect to spend a lot of time nursing in the early days, so try to figure out what you can do with your other LOs while the baby is nursing -- maybe someone can help, maybe you'll have some new toys/movies for them, maybe your significant other will be around to help.
Most moms have enough milk, unless there is some sort of medical reason why not -- the absolute best thing you can do in the early days to get that milk supply established is to nurse a ton -- as in somewhere around 10-12 times/24 hours. Once your milk supply gets going, you should be in good shape. As for gas, make sure you burp really well after feedings -- actually, I would wonder if you had one baby with latching trouble and one that was very gassy, if overactive letdown/oversupply was an issue for you. Did you feel like you had milk shooting out of you when your LO latched on? Sometimes that makes it harder for LOs to nurse, though if you're aware of it, it's easy to work around.
Good luck!
