personally, i would never use conventional oil in any Lexus product, given how easily the can sludge the oil. spark plugs are done at 120,000 miles. you really want a local Japanese specialty shop to do ALL your work if you want to keep the vehicle long term. sure, they will charge more for an oil change, but they are tons better and more qualified than anyone at Goober Lube!
Depending on where you get your oil changed, it could be as little as $19.95 or as high as $50. A good comprehensive tune-up could range anywhere from $250.00 to $400.00 depending on how much needs to be done.