Just post a little, let folks get to know you around the forums, and get a couple of deals under your belt and you'll be fine. There's been an influx of scammers lately so it's got folks being more cautious lately is all. You'll do fine. Good luck on your purchase later.
Welcome! It's great to get the perspective of somebody like you who as a new citizen loves this country more than some of the people born here! On top of that, since you became a legal citizen you likely have more knowledge of this country than many natives do!