Okay well here is the latest. I went to Auto Zone today and got the code. It is PO128. The same one that was recently posted. The guy at Auto Zone told me the same 2 things...Thermostat and Head gasket. My husbands buddy at work says it is probably the thermo. since they checked the radiator and the coolant level hasn't changed. When I run the van the thermo. stays right at 160, the lowest level. I had it running for probably an hour today and it never got above that number. I hope this can shed some light and you all can help!
Thanks for all the help so far!