You need to ask an attorney. We have no idea of the documents involved, nor most of us attorneys practicing in Illinois. Sometimes when posters ask questions like this on Trulia a well-intended, but incorrect, answer could really cause you some trouble.
If it is not in a trust then yes, Mwass would be correct.
if the property is owned in a trust (as in carl's scenario) the trustee signs the deed.
if the estate is in probate and is an "independent administration," the administrator/executor signs the deed.
if the probate is a "supervised" administration, the administrator/executor signs the deed, but needs a court order to sell
if there is no probate of the estate, all the heirs should sign the deed.
I just finished selling a property for an estate where I am the executor. All my Realtor asked was for a copy of the living trust where it showed that I was the executor.
Pretty simple process. The proceeds of the sale will go to the living trust account which the executor should have already set up. If the estate is not in a trust then I believe that it will go through probate and then the State gets a piece of the action.