Yep, sounds like replacing thermostats, is a good first start. As you mentioned, they are probably stuck open, or at least one of them is. (I assume, you will have the 2 thermostat style of housing, because you mentioned 2002 model)

Hopefully, your "stud bolts"(housing mounting bolts) aren't corroded inside the aluminum housing, if so, that makes it more difficult to remove.(recommend new bolts if they look corroded , in the least little bit)

Don't forget to install new lip seals and "stake" them in. I use a automatic center punch, to put some dimples, around the aluminum bore, after I installed each new lip seal. (I just use the correct size to 3/4" drive socket to tap in the new lip seal (= I think it is my Craftsmans 2" chrome 3/4" drive shallow socket that works, for me).

 Dimpling that bore surface a little, helps insure that lip seal doesn't get loose, in its bore, when the engine gets up to operating temp.= if that happens, then it overcools AND overheats.(Depends on engine load, which condition happens)

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CATc12withdualthermostathousing2.jpg (107KB - 147 downloads)

lip seals inside thermostat housing2.jpg (59KB - 114 downloads)