Both are reversibe AFAIK and you are a newbie with 1 post. So yeah, proceed with caution
Exactly, caution is needed, these are very risky ways to buy Bitcoins and 3 BTC is not small amount. Besides, you are newbie without reputation so it will not be that easy to find a forum member to trade with you. Have you maybe considered some other options and payment methods, maybe localbitcoins?