Changing the fluid in the differentials of your Jeep 2000 Grand Cherokee AWD is a good maintenance practice that can help prolong the life of your vehicle's drivetrain. Here are the steps to follow:

1. Gather the necessary tools and materials: You will need a socket wrench set or a ratchet and socket, a breaker bar, a drain pan, a funnel, a container of the recommended differential fluid (usually gear oil), a clean cloth or rag, and safety gloves.

2. Locate the differential units: The front and rear differentials are usually found underneath the vehicle, behind the engine and closer to the wheels. The front differential is located on the passenger side (right-hand side) of the vehicle, while the rear differential is at the center or towards the rear.

3. Prepare the vehicle: Ensure the vehicle is on level ground and engage the parking brake for safety. If needed, use wheel chocks to prevent the vehicle from moving.

4. Drain the old fluid: Place the drain pan underneath the differential you wish to work on. Locate the differential's drain plug, which is typically a hex bolt or a square-headed plug at the bottom of the differential housing. Loosen the drain plug using a socket wrench or ratchet, accompanied by a breaker bar if necessary. Slowly remove the plug and allow the old fluid to drain fully into the pan.

5. Inspect and clean the drain plug: While the fluid is draining, inspect the drain plug for any metal shavings or other debris. Clean the plug with a clean cloth or rag and set it aside.

6. Replace the drain plug: Once the fluid has completely drained, clean the drain plug hole with a cloth or rag. Apply a small amount of thread sealant to the drain plug (if recommended by the manufacturer) and securely tighten it back into place.

7. Refill with new fluid: Locate the differential's fill hole, which is typically situated higher up on the differential housing, either on the side or on top. Depending on the differential, a fluid level check plug may also be present. Use a funnel to pour the recommended differential fluid into the fill hole until it starts to overflow from the check plug hole (if applicable). Use the appropriate fluid quantity specified in the vehicle's owner's manual.

8. Reinstall the fill hole and check plugs: If there is a separate check plug, reinstall it securely using the necessary tools. Tighten the fill and check plugs, ensuring they are properly sealed to prevent leaks.

9. Repeat the process for the other differential: If you intend to change the fluid in both the front and rear differentials, repeat steps 4 to 8 for the other differential unit.

10. Clean up and dispose of the old fluid properly: Once you have completed the fluid changes, clean any spilled fluid and properly dispose of the old fluid at a designated recycling facility or consult your local regulations.

It is important to consult your vehicle's owner's manual for specific guidance, as the process may differ slightly depending on the make and model of your Jeep Grand Cherokee. Additionally, it is always recommended to use the manufacturer-recommended fluid and to follow the suggested service intervals.