My check engine light came on yesterday. What could this be? What parts should I replace to remedy the problem?

98 4runner 82,000 miles.

Take it to the dealer for analysis.

could be a number of things, most common are going to be oxygen sensors, throttle position sensors, etc, but take it to a shop and see what code it is outputting and go from there, dealer would be the way to go, between warranty and recalls , check it out,