Toyota Repair: tune-up, engine coolant, toyota camry

Question
I've lost my '99 Toyota Camry's V 6 owner manual and would like to know when I need to have a tune-up on the car. I had one done 5 years ago. What parts need to be changed now that I have close to 100T miles on it. When does the timing belt absolutely need to be changed? Can they look at it and see in what condition it is in? I  also have the check engine light on and am getting an emissions code. One mechanic said I needed to change the charcoal cannister and another said thqat I needed to change the gas cap which is what I did with an aftermarket cap, but the light stayed on. Should I try a Toyota cap first. Thanks

Answer
The spark plugs should be replaced at about 60,000 miles, same for the transmission oil and the engine coolant. The timing belt should be replaced at 90,000 miles. I can help with the check engine light code if you can give me the diagnostic trouble code number. You should always use a direct replacement gas cap from the dealer to be sure, some of the aftermarket caps may not seal or vent correctly.