bree

Hi I am new to the forum. I own a 1999 Sienna with 210,000 miles. It has been the best van and still is.... But, just recently the engine light came on. It is not running poorly. I brought it to Advanced auto parts to read the code and they said it might have been some bad gas? My friend said it might be an oxygen sensor? My question is how do you know and how hard is it to change out an oxygen sensor? Any input helps, we are not getting a new car anytime soon and would love to just fix what we have. Thanks, Bree