On the top of firewall on passenger side of engine bay.
A '96 jimmy does not have a body control module (bcm), it does, however, have an engine control module (ecm) located ontop of the coolant reservoir.
Its on top of the trans as you're looking down. Its not internal. I've replaced mine on my 1997 Sable.
On a 1996 Mercury Sable : The automatic transaxle ( transmission ) fluid level dipstick is near the firewall and the brake fluid reservoir ( looking from the FRONT of the vehicle it is to the left of the reservoir )
It takes R134a, which is the new EPA "standard" freon.
According to the drawing in the 1996 Mercury Sable Owner Guide : The fuse panel is under the dash by the brake pedal Also , the Power Distribution Box ( which is " live " ) is located in the front of the engine compartment , near the battery
The CCRM on a 96 Sable is attached to the left side (drivers side) of the battery tray. Undo the spring clamp to remove the CCRM from the tray. The electrical harness on the CCRM is short. If you need to remove the harness, first remove the battery, then remove the battery tray, then you will have room to rotate the connector to expose the 5mm nut that you must loosen to remove the harness connector.
The 96 grand am does not have a body control module according to the dealership parts dept. It does however have a brake control module that is located in the firewall about in the center of the cowl area right next to the blower motor.
Your local auto parts store can help you with that.
3 gallons which should be a 50/50 mix of anti-freeze and water - 1.5 gallons of each.
Its beside the rad. on the drivers side
The body control module serves many functions. The BCM operates door locks, security systems, headlight dimming, among other functions in the vehicle.
Serpentine / accessory drive belts price around $15-30.Don't go cheap on this particular item.See "Related Questions" below for tons more about Sable serpentine belts.