Mazda Forum - Mazda Enthusiast Forums - *96 Protege-3 probs: ck engine lite, AC, squeaky wheels

1996 MAZDA PROTEGE DX, 1.5L 5 spd., 110500 miles
I'm a GIRL with limited funds and knowledge.
Problems:
The check engine light goes and stays on.
I took it to CheckerAuto and their machine said the problem was: EGR booster sensor. An acquaintance pulled the clip out of the sensor, removed its hose, blew into it and put it back together. This made the light stay off for about 1 hour.

a. can one get a EGR sensor from a salvage yard? IF so, will all 1996-1999 models be potential candidates to take one from?

b. Or, does one need to by a remanufactured one instead? Or, an aftermarket one? Do you know of reasonable stores?

c. Can I just unscrew the part, pull its clip and hose and install it myself?

d. Something I read mentioned carbon buildup in the throttle body as a problem. Is this something a CheckerAuto employee can point out and I could clean, if he directs me? Or, is it buried and not easily accessible?

e. Also there is a high pitched squeak when I turn the car wheels while driving. It seems to be in the front. What MIGHT that be?

f. If the squeak is the brakes, does that mean pads or pads, rotors and calipers? I bought the car used and don't know how old the breaks are.

g. the AC blows, but is faintly cool. I had a can of the new type Freon put in it. How often does one need to repeat that? It helped a little but not as I had hoped. Is my AC going bad? What MIGHT cause whimpy cooling?

I do have an acquaintance that can do some simple things for a car.
Thank you.