Ok, Mr. Dick.
The difference is the resolution....basically more accurate reading. Unless you're running nitrous or turbo there is no need for it. The money is a total waste just to make the a/f gauge read better. Go with the heated Ford Escort sensor....someone here knows the part #.
For the second question....I have no idea where to get one. Why don't you try
www.widebando2.com, even an idiot could figure that out, but obviously a dick can't. j/k