This is a big job. You're going to want a shop manual that gives you all the required steps and photos. Haynes or Chilton will probably do just fine.
Remove the transmission oil pan
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* Remove the front bumper fascia * Unplug the horn electrical connector and remove the bracket bolt
You must first remove the trunk door facia. (This is the part with the "Pontiac" lights in it.) Then you can get to the bulb to replace it.
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I need to know how to remove a rear wheel speed sensor on a 2002 Pontiac Sunfire
remove both hoses and replace the o rings
It's hard to be specific here. Go to your local parts store and pick up a Chilton or Haynes manual for your car. Either one will have very good directions with pictures.
The flex plate is bolted to the back of the crankshaft. It connects the motor to the torque converter in the transmission. To replace you remove the transmission and replace it.
Remove the serpentine belt. Tensioner is below Alternator. Remove the three mounting bolts on the tensioner baracket assembly. Replace entire unit.
Remove the panel under steering wheel. There will be 2 flashers. Replace one on right.
Remove transmission oil pan Replace fluid, filter, and gasket