2006 ISX thermostat replacement

I bought a 2007 International 9400i a couple months ago. The thermostat seems to stick when first warming up. As I don't have maintenance records I thought I would replace the thermostat and the coolant while I am at it. I have been searching the internet all night to try to find out what gaskets I need to do this. I see some diagrams that show a thermostat housing gasket and a seal. Then I see other diagrams with two seals and two housing gaskets, one on the engine block and one between the two parts of the thermostat housing. The other thing I ran into was the thermostat itself. Apparently the original thermostat was a bad design and was superceded by a cooler thermostat (180 degrees)? Does anyone know anything about this that would be willing to help a new owner-op?

Thanks,
Cliff