XG300 - Back to Dealer

I was going to change the plugs, wires and plenum gasket of my 2001 XG300 but when I saw oil on the plugs, I realized that I am in an area where I don't belong.
So, this morning, I brought the car back to the dealer and asked the service manager to check it all out, change the plugs, etc, change the timing belt ($650 not bad) and he said he'd change the drive belts once the car is apart and there would be no installation fee, I also asked him to check the water pump. I think my trip back to my youth had to end, as glorious as it felt. Besides, my daughter is getting the car and I want to limit the chances of problems as she might be moving to Washington State with it.
The $510 I was quoted was with changing of the plugs, wires, gasket, pcv valve and air filter. I couldn't find the receipt for the diagnostic fee until yesterday and there I saw the other two items, which really does bring the cost more in line. I did replace the air filter, with a Framm filter, that maneuver I was able to do. I could have probably done it all except for the leaking oil into the plug cylinders. www.hmaservice.com has very good information and pictures to let you know where things are like the pcv valve and the throttle body. However, the time that I was consuming on learning everything from scratch only to be able to change minor things, after the plugs and wires were replaced, was not worth the effort. Hopefully, I won't regret it when I get the car back.
I do believe the plugs were Ok and were really never the problem directly because performance was so good, But it must have been coincidence that the oil got into the plug cylinders at the same time the battery went. The service manager at the dealer has the most sincere facial expressions but until I saw the oil I didn't believe him or thought he was just wrong. The diagnostic code was P0303 #3 Misfire.
Alan
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What is a transmission Cooler? I supposedly need that for $600?
Mine is almost all rotted out, as they say.
wrote:

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It is like a radiator that cools the tranny fluid. They can deteriorate over time but how do you know it is "almost" rotted out? Is it leaking?
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I have never seen this. I've seen a few leak, though.
Stuff like this occurs because mechanics cannot be bothered to actually tell advisers why stuff needs to be done. So the advisers make up some crap about why it's needed. My guess would be that it's leaking.
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