How to install a CD deck in to a 1994 ford explorer XLT?

Here's a good link: http://www.installdr.com/

Should be little holes in the face of your factory deck... you can go buy the special little tools to put into these holes and the deck will slide out.

I believe that is 19.3 U.S. gallons

it on the blower motor housing

A 1994 Explorer has 2 oxygen sensors, they are either screwed into the exhaust manifolds at their outlets or into the ehaust pipes near the engine.