Only his estate can be used to pay creditors, you will not be personally liable. So, you have nothing to lose.
If your dad has claims that are still valid against your dad, his estate can be liable for them. However, there is a statute of limitation which varies by state (6 months in IL) after which claims are barred. To bar the claims, you have to both publish in a newspaper (according to state rules) and specifically notify any "known or reasonably ascertainable" creditors. Your probate attorney can explain the process more specifically.
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Jeffrey R. Gottlieb, Attorney at Law
http://www.illinoisestateplan.com
This response is not legal advice and does not create an attorney-client relationship.