I'm also a first time mom, and I just switched my 10 week old daughter to Similac Sensitive. She was on Enfamil Newborn, along with several other formulas before that, and had bad gas. I kid you not, she could clear a room. My aunt suggested I try a different formula because the gas might be caused by the lactose. Similac Sensitive has low amounts of lactose in it, and her gas has gotten a lot better. When she does pass gas, it no longer smells and it's a lot less often.
Your baby's immune system might not be able to break down the lactose yet, and that might be the cause for the smelly gas. Similac Sensitive works really well and might be worth a shot.