Toyota Repair: Oxygen Sensor, camry xle, technical information systems

Question
Hi Ted
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
This sensor is located on the exhaust manifold, look at the front exhaust manifold near the radiator there is one identical to the rear one, it looks kind of like a spark plug and has four wires inside an insulator coming out of it which are connected to an electrical connector. The sensor in the rear is in the same location but because of components like the subframe and power steering gear and pipes and a motor mount it is very difficult to remove without some tools including a specail o2 sensor socket, yes there is one just for this purpose.
Since the problem is already diagnosed and you know what needs to be replaced why don't buy the part and ask the toyota dealer how much they charge to install it, you may be able to save some money this way.
I have worked for toyota for more than 25 years and have just about dealt with everything there is, technology is changing faster than we can keep up even at the dealer level but we manage, toyota has an excellent technical information systems on the internet with new information and bulletins coming in on a daily basis.
I deal mostly with diagnostics and driveability problems,which is what I like the most other than that I do normal maintenance type of work.