Help with YTD sales data comparison from two years - need to match and compare

I have two sheets of data with sales figure totals and quantity shipped based on company names. I have one sheet for 2012 and one for 2013. I need to put these on one sheet and then compare the sales data. I have some companies in 2012 which are not listed in 2013 and some new ones in 2013 that were not in the 2012 sheet. I don't know how to merge these two sheets together into one matching up companies names that are identical and then get the +/- calculation for the sales comparison and the quantity shipped. The attached example (sheet3) is how I want the final sheet to look. HELP!! Thank you!!