2010 Q1 Tax Estimate - LLC Member?

Hi, I am trying to figure out what I owe for my Q1 federal tax estimate for 2010. I am a member of an LLC who owns 50% of the company. I understand that I have to pay 15.5% for self employment tax, but I am confused beyond this? Everything I have read says that you need to refer to your 2009 tax return and do some calculations to figure your average tax rate. Thing is, I filed jointly with me wife last year and had no US income because I moved to the US from Canada in November. So, I have no idea how to figure out what my tax rate would be. In short to figure out what I owe I need to multiply my earnings from the LLC by 15.5% and then multiply that number by my tax rate (I need to figure out what number that is). Thanks for your help!