You need to check with a tax attorney. However, the "death tax" was repealed over time ending in 2005.
Basically, if you inherited over $1,000,000 in 2002, you had to pay federal taxes on it. That amount went up to $1.5 million if the death occurred in 2003-2004. If the death occurred in 2005-2006, you should owe nothing to the IRS for the inheritance.