The 2SD movement is (eventually) going to be a long column/post, that's fairly detailed. As for calculating option prices in the future there are two methods:
1. Option Calculator (the better way). I like the CBOE's but there are many (http://www.cboe.com/framed/IVolframed.aspx?content=http%3a%2f%2fcboe.ivolatility.com%2fcalc%2findex.j%3fcontract%3d2B727374-766B-4CE9-87DE-EF77AEEF4D51§ionName=SEC_TRADING_TOOLS&title=CBOE%20-%20IVolatility%20Services)
2. Or you can just go look at historical prices with 28 days left to get an approximation if IV levels are close to the same (I SOMETIMES do this when first glancing at a potential trade because it's quicker, but I never rely on it).