I have a 2004 Dodge Ram with the 5.7L HEMI the engine light is on and I found out it is the oxygen sensor,There is a total of 4 of them I think, Is there any way to tell which one needs replacing? They are a bit pricey, I also just found out a pair of front brake pads will cost me $40! My last dodge, they were $14. Will it hurt the engine to drive with a bad oxygen sensor for a little while? I really hope I dont have to replace all of them!