how much is cost to fix gasket and o2 sensor? for good parts and labor?

I think head gasket, and yes the engine light is on. no perfomance issue just bad smell from leaking gasket, and mechanic thinks sensor will help the car run better and get better milage.

For the 2002 Montero 3.0 you have two head gaskets for the right side gasket labor time calls for 7.4 for the left 8.1 for both 10.2 hours in labor. On the issue of the O2 sensor .. I wouldn't be comfortable taking his word if he just "think's" it will fix it.

thanks, I told him to just fix the leak first. to worry about the sensor later. How much do you guys think that labor should be for this? he told me $100 for gasket. he quoted me $150 for sensor but estimated on the high end $3-400.00 for all that and labor, but now I told him to just fix the gasket. How much do you guys think that should be? He is a friend of mine and will be fixing it at home, but we have been on a bad note for a bit and for some reason I feel like he is trying to stick it to me.