Dear Tom and Ray:

My 1995 Honda Civic has been diagnosed with a bad oxygen sensor. Although I am not mechanically inclined and have almost no tools to speak of, I've been entertaining the idea of replacing the little sucker myself. Short of providing entertainment for my neighbors, is it a reasonable thing to do? Or should I sell biscotti at the local farmer's market instead until I raise the $211 it would cost to have it done by a pro? -- Leonardo

TOM: Well, if you had to pick a job to start with, this would be a pretty good one, Leonardo. It's really fairly easy, on this car.

RAY: The oxygen sensor is right up front, just behind the radiator. You'll find the sensor threaded into the exhaust manifold, and there will be one wire coming out of it. Unplug the wire, and then -- using a 7/8ths wrench -- loosen up the sensor, unscrew it and remove it.

TOM: Then, in the opposite order, put the new one in and reattach the wire. If your check-engine light is on because of your bad oxygen sensor, it'll reset itself and go out after a while. That's all there is to it, Leo.

RAY: However, if any of the following situations occur, you should fall back to plan B ("B" for "biscotti sales"): (1) You are unable to open the hood. (2) You are unable to find or identify the oxygen sensor. (3) You are unable to remove the wire. (4) You are unable to loosen the sensor. (5) You strip the sensor because you didn't use a 7/8ths wrench, like we told you to. (6) The wrench slips and you bust a hole in the radiator while trying to loosen the nut.

TOM: But nothing ventured, nothing gained -- right, Leonardo? We'll be pulling for you, buddy.