91 4Runner v6 CEL code 12 and 25

[go_dawgs]

I have a 91 4Runner V6 that began running a bit sluggish and seemed to skip a little accelerating from a stop. Timing belt was changed not to long ago. I am getting codes 12 and 25. Wondering if I should try an new 02 sensor or if I am on the wrong track. Home on a break from the military overseas and hoping to get this thing back to normal shortly so I will have transportation.