Well in that case any ethylene glycol mix will be better! If you're basically going to be doing a flush, no point in wasting expensive red stuff for that.
Re the thermostat, I haven't taken mine off yet but it looks straight-forward on mine, no reason to think the 12V would be much different.
Drain the coolant, undo the 2 bolts holding the inlet hose onto block and the thermostat will be sitting in front of you. Don't think any special tools or techniques needed to remove it from the hose/head
EDIT: Just looked it up on the FSM (RM437E for HD-FT) and it's page EG-184. Says there that there are 3 bolts to undo - the 3rd one secures the hose onto the body.
Just a general, maybe useless, comment - the 4.2 seem to be over-cooled, i.e. the rad easily copes with the cooling load. There are stories of lots of guys running all winter with the rad blind down, which blocks most of the airflow into the rad so it just the fan trying to circulate air within the engine bay, and no problems guage normal. I know Ian's green truck actually gets cold at idle - after driving around at normal temp, the guage starts to drop as idle. Maybe his thermostat is stuck open but you get the point that overheating isn't a major threat unless something is seriously wrong (blockage or coolant all leaks out). Coming from a KZ-TE I think you'll be on top of any cooling issues anyway
Cheers,
