Tune Up on 99 Lexus RX300

Just wondering who out there may have a clue as to doing a "do it yourself" tune-up on the 99 Lexus RX 300. I called the dealership and the price is outrageous ($400.00). I also asked their parts department about the type of spark plugs and basically you can only buy the manufacturer, dealer only, plugs which run you close to $20.00 each. I then asked the service dept. about other types of plugs and was told to make sure and use only a platinum Lexus approved plug. When I called around to the parts houses, I was only given one brand of plug, the Autolite already pre-gapped. So, can anyone out there tell me where in the world I find the plugs on this vehicle and how do I take them out. I can handle all other matters regarding the tune up as I familiar with cleaning out the throttle body and air cleaner. No fuel filter to replace as it is in the fuel tank and it never needs to be replaced according to Lexus....Thank you......JB