Do I need to file Form 706 Estate tax with IRS?

You do not need to file a 706 if his estate was only $100000.

You will not need to file a Form 706 if your husband and his estate did not exhaust his lifetime gift and estate tax unified credit. More info is available here: http://www.irs.gov/publications/p950/ar02.html

My colleagues are correct the value of the estate is under the required amount for the federal 706 return. You will have to file a pa inheritance tax return. Additionally, if income has been produced by the estate assets the estate may have to file a fiduciary income tax return for Pa and the Feds. See IRS form 1041 for more information.

While I agree that you do not HAVE to file. Some attorney advise filing anyway to preserve what is called "portability" - were you to come into serious money (more than 5.5 million or so) during the rest of your life, filing the return now would preserve your ability to use his estate tax exemption. Many attorneys, if filing the PA inheritance tax return, can easily file the 706 as well for very little extra cost. It is an outside chance that you would ever need it, but it has a small chance of potentially saving you hundreds of thousands if not more of estate taxes.