2000 Sienna Check Engine Light

Check engine light came on. Dealer said it was oxygen sensor. Can I just the sensor or do they need to change spark plugs and other things in order to get light to reset?

Dealer wants to change several parts to reset light.
sensor, spark plugs, etc...

Ask the dealer about Engine Sludge and ask them to do a check for it. Other signs of sludge are smoke in the exhaust on first start up, high use of oil -- greater than 1 qt. per 1000 miles, and thick oil on the dipstick. Even if you just have light coming on, Toyota is supposed to do a free check for sludge. Call their sludge hotline. You can find the nubmer at http://www.autosafety.org