Toyota Repair: Oxygen Sensor, camry xle, oxygen sensors

Question
Hi Paul
My check-engine-light came on and Goodyear's diagnostic confirmed one of my oxygen sensors is bad. Said I have 3; bad one is on the back side of the engine. $167 parts, $183 labor. Unless you advise otherwise, I'd like to fix it myself. I'm certainly no mechanic but I've replaced starters, alternators, exhaust manifold before.  But I don't even know what an O2 sensor looks like. Can you tell me approx where it's located on my engine, what it looks like, do I need any special tools/equipment to remove/replace? It's '94 Camry XLE, 3.0L 6 cyl, engine type 1MZ-FE, 147,000 miles, owned it 18 months. By the way, I envy you "mechanical" types. Wish I had that ability. (I'm in telephone sales to large corporations). I think it would be fascinating working on cars all day. Would be interested in how you got started and what type of mechanical problems you like to work on most/least.  
Thank you.
Don

Answer
how are you and thank you for writing. the oxygen sensor you are talking about is located on the exhaust manifold at the rear of the engine(firewall side) about halfway down. you would need a 7/8 wrench and some rust penetrant to do the job. it is easiest on a lift so you can get to it..
i started when i was 16 working on my own vehicle on my back in the driveway and just started off changing oil at a car dealer and worked my way up.i enjoy working on the crazy electrical problems and the check engine lights the most.. cause you never know what to expect. it's a challenge. i hate doing regular maintance the most cause it's repitious.