unless you absolutely have to, let it cool a couple hours before starting on it. IF you managed to get the cap off while it was hot, the force of the gushing boiling water would seriously injure you....for life.
If it is running hot, the radiator has probably already boiler over at some point. probably would not need to dump fluid.
Replace it with a stock thermostat unless you live in an area where it needs to run hotter and top off the fuild.
On the other side, if you have not replaced you fluid for a while, now is a good time.
If the thing is still under warranty, dont bother. go to the dealer, go to lunch,come back, tada! it's fixed!! wish it was that easy....
Benjamin Davis Pirtle