Toyota Repair: Tune up time for 200k 4Runner, k n air filter, drive belts

Question
The old '97 just turned 200k and its time to do some service.  I'm pretty much the "if it's not broke, leave it alone type," but the 4Runner is really asking for a tune up.  I bought it at CARMAX with 58k on the clock, so I have no idea what its early service history was.  I have done the following:  100k - new Bilsteins all round, a K&N air filter, rotors and pads myself.  150k - replaced the contactors on the starter ($13.00 part) myself.  170k - had the stealership do that rear suspension recall and the timing belt while it was in there.  Of course they told me that the water pump was shot and leaking all over the place and they'd be glad to replace it for $400.00. NOT, I told them to put it back and haven't had any problems.  180k - replaced the original battery and did the front pads and rotors again myself.  That's it except for oil changes and tires.  I've never even pulled a plug. The truck still looks great and I expect it to last another 100k.  I've way pushed the limits on maintenance though and the 3.4L is starting to get a little pinging when pushed hard.  I'm starting to gather parts for a major tune up.  I'm thinking new plugs, wires, fuel filter, pcv valve, drive belts, change coolant and clean the throttle body.  What else should be done in the way of general service at this point?  The transmission dipstick looks clean.  Any reason to do all the fluids - trans, transfer case, axles?  Any other replaceable parts that are bound to give at some point?  I'm not looking for work, but since it's so rare that I have to do any wrenching on this vehicle, I'd rather do it all at once!  

Answer
You've pretty much got it covered with the tune up parts, nothing really goes wrong with this engine when maintained, the only other thing I would recommend is changing the transmission fluid and the coolant. I also recommend that differential fluids on both differentials and the transfer case be replaced if they have never been changed as long as you have owned it. These fluids do break down after a while and you will see what I mean when you drain the differential, some transfer cases use ATF and some use gear oil, so make sure you identify what comes out of the transfer case, the differentials use normal 80-90wt gear oil unless it it limited slip, if so it will say on the differential and you can use LSD oil or regular oil and an additive available at the dealer or autoparts store.