As usual, the check engine light is on. took it to pepboys and my oxygen sensor in the front right is out. Had bad gas mileage b4 that and thought something was wrong. going to have to fix myself 'cos the want $300 to fix the damn thing.

Couple of questions.

1) Does bad oxygen sensor lead to bad gas mileage and how much difference does it make.

2)Going to have to fix myself, on a scale of 1-10, i need difficulty level

Any help would be appreciated. thanks

 

1) Yup, alot especially the 2 front ones
2) Maybe 7-8 because of where it's located and it might be stuck