Go to YouTube.com and type in rear speaker replacement Saturn. A guy did a video explaining each step in removing stuff to gain easy access to the rear speakers. Here is the link: http://www.youtube.com/watch?v=x4mchytppo8
In order to replace the speakers you have to flip down the rear seats and look at the screw ports and remove all the screws to remove the panel covering the speakers. The rest is self explanatory.
If its a convertable, remove the the screws under the rear seat and remove. Then remove the screws holding the leather enclosures and remove from sill plate. remove the speaker boxes and replace. If you don't have new speaker boxes remove cover a speaker box, access speaker and replace, you will probably have to solder the wires, then reverse the order and put back together.
Pop the cover off and unbolt (or unscrew) the old ones, unplug them and replace in reverse order.
If you're talking about a Focus, there is a panel in the trunk area.
Remove Trunk Carpet. Remove 3 Phillips bolts holding cover. Remove Clip and Hoses. Unscrew larger ring holding down pump. Remove and Replace in reverse order with new pump.
change it from the inside
you have to remove the whole door panel in order to gain access to the factory speakers in which should be 4x6.
The door speakers are 5.25 inches but you have to purchase an insert in order to replace the door speakers.
Crank position sensor is located next to the crankshaft. In order to replace it you might have to remove the timing belt. In the most models you just can remove remove the timing belt cover and replace the sensor.
You change them from the INSIDE.
In order to remove the screws that secure the rear speakers, you need a 7/32" socket and socket wrench. The wiring harness I have yet to figure out how to remove from the backs of the speakers lol.
You will need to remove the front engine cover, on your 1997 Pontiac Bonneville, in order to change the supercharger belt. Loosen the tensioner pulley to remove the belt.