97 Plymouth Neon alternator belt is slipping is this hard to fix or expensive?

Fix ? You mean replace ! An not hard to replace , may need special tool's to do it . Look on youtube , may be a video showing how to do it. How to Replace Fuel Filter on 1997 Neon Plymouth

Timing belt slipped a tooth, stuck valve, plug wires crossed, or a very lean condition.

I suggest not driving it until the timing belt is inspected or replaced

one of two things, belt is old and stretched out and slipping over pulleys, or you have a bad bearing in your alternator or other accessory. or one of you accessories (such as a power steer pump) is starting to go out and having a hard time turning causing your belt to slip

Have your belt condition and tension checked. The alternator works harder with those accessories on, thus a loose or faulty belt will squeal.

CHECK ALTERNATOR DRIVE BELT TENSION MAKE SURE ITS NOT LOOSE SHOULD DEFLECT 0.35 TO 0.45 INCH. IF NOT ADJUST DRIVE BELT TENSION.IF ALL IS GOOD CHECK ALTERNATOR OUT PUT VOLTAGE AT CAR BATTERY.IT SHOULD BE 13.5 - 14.5 VOLTS. IF NOT.ALTERNATOR FAULTY. CHECK ALTERNATOR FUSE AND CHECK B+ WIRE AND FIELD WIRES FOR LOOSENESS AND DAMAGE.

It sounds like you have a belt or pulley problem, or possibly a bad bearing in the alternator, or water pump. I would suggest, having it looked at, by a mechanic right away.

Sounds like a timing belt has broken. If you are lucky it has not done more damage. Best to hook up a code reader and see if it is reporting missing cam sensor. If it is, the timing belt is broken.

the altenator belt in on the passenger side of the engine beside the passenger inner fender
thanks for choosing FIX YA !

Both your air con and defogger (I am assuming you mean front windshield defroster setting, and not the back window) engage the air conditioner pump/compressor.

The screeching can be either a bad belt or a bad compressor.

How long has it been since the belt was changed? If it is old, and slipping, it will cause the screech at speed.
If the belt has recently been changed, and is adjusted properly, I would start looking that the air compressor pump.

You may need a new serpentine belt tensioner. That's the part that keeps the belts tight. If it's weak, it may be allowing the belt to slip. When you say the car runs "hard" what exactly do you mean? That the RPMs dip down when you turn on the AC? If so, that's normal since the AC compressor loads the engine pretty heavily. If you mean something else by it, please repost and clarify what you're seeing/hearing so we can take it from there.