Just did the swap last night. It was kind of a disaster but that was my fault. Don, I would recommend doing it since mine had not totally failed yet but the gasket was almost half off the thermostat. No joke they do start peeling off like LRNA says. Mine was running fine but I really wanted that peace of mind, and I am glad that I did it. Make sure if you get it from Graeme/whoever that you get the tiny gasket for the cover too.
I had the thermostat, and the new gasket for the housing cover, cost $77 at dealer, with a gallon of LR XLC coolant undiluted in case I needed more coolant (I ended up just using 50/50 Prestone Dex-cool that I had around the house since it was late when I finished and I had no patience for messing with any more coolant)
Did not remove thermostat cover (the piece that holds the t-stat) from the engine bay and instead tried to work on it there with the hoses still connected (in an effort to make it easier). I then proceeded to drop the tiny thimble that seats the thermostat head, somewhere into the engine bay. Cue 3 hours later, took apart front end, shields, plastic trim, coolant bottle, front headlights, nothing. Fortunately parts man at dealership here helped me find a replacement part that contained this tiny thimble piece and so I paid a very expensive lesson for my mistake.
Get home with new part 20 minutes later, now dark outside. Proceed to try and reassemble t-stat, which I know now to be nearly impossible since it will be upside down and you need considerable force to compress the springs enough. I decide okay I'll try this another way, take thermostat out, but the thimble thing slips off the end of the spindle.... INTO THE RADIATOR FEED HOSE. THATS RIGHT THE GIANT HOSE THAT FALLS THROUGH THE ENGINE BAY AND INTO THE RADIATOR. Now my radiator and or hoses are now holding this tiny metal piece inside. I freak out, and immediately think the world is going to end. Not only have I lost the same part twice, this time I know where it is and if I cant get it out it will probably break something.
I pull the radiator tube, coolant flies everywhere, all over me, a few pads, and the ground, which is muddy leaves. My coolant drainings in a clean pan are now ruined from dirt and leaves. BUT THE THIMBLE CAME OUT. I cried tears of sweet sweet joy and proceeded to immediately bag it up for safety.
Took all parts needed from engine bay. Reassembled T stat in kitchen. Reinstalled all hoses and t stat, including O ring (which I would replace btw since its only a dollar or so). Filled coolant from new bottle, then burped the system which took a while but is not actually hard. the IID tool was super nice for telling all sorts of stuff, like coolant and oil temp, and engine and fan speed in rpm.
LONG STORY SHORT
If I knew what I was doing and hadn't been lazy or not focused on how important some parts were I could have knocked this out in minutes. It is literally that simple. I added a good 5 hours of work/searching/disassembly/crying because I lost two of those tiny thimbles, the second time necessitating a draining of the radiator.
remove engine cover
remove bleeder tube outlet from T stat cover and let some coolant drain from that location
remove 3 screws holding t stat cover
remove the other two hose clamps and hoses from t stat cover
take inside and swap thermostat, make sure you swap over tiny thimble thing (AKA xanthor, destroyer of wallets)
remove and replace gasket @ engine with some tiny pliers
replace cover with new t stat on engine with the 3 screws
fill coolant system
fill as needed
get engine to 198-210F(which is where thermostat opens)
shut down, let cool, check coolant level
add coolant if necessary
do process one more time