Ok from what I have heard breastfeeding is do able after getting pierced so dont worry. I just got mine done about 3 weeks ago by a guy who wasnt liscenced and didnt really know his stuff, so the first thing I would say is to do your reasearch and make sure that the person who does yours is a liscenced pro who knows what they are doing!! There is another thread on the ladies lounge on nipple piercings that you can read with more info on the topic... and a link to a great site too. Good luck and go for it you will really love it... it doesnt hurt at all!
Oh yeah and I have heard that 14 gauge is the industry standard for nipples...