This.
Best guess, you will get something back at year end from the Feds. Depends on your wife, and other deductions, etc.
My suggestion is just fill out the w-4 form the way it's written, and you'll generally come out ok. If you really want to double check, some online tax prep software is free (taxslayer comes to mind, or go to irs look for freefile). You can always put your income/exemptions/deductions into it for 2012, see what it says. I don't think there will be many major changes for 2013.
Goodluck, taxes are tricky! As for Ill. not familiar, same thing though, fill out the state witholding form the way written, and usually come out ok.