Thank you so much M.B.Doc and Smiffy6four for responding and helping
I really appreciate it.
I did some more search based on the info you guys provided and I hope to get more specific info to the 2002 ML 320 I have, as I am no expert like you guys and will have to follow them to the tee in a step by step monkey see monkey do fashion


Step 1 Secure the vehicle with the emergency brake.

Step 2 Chock the rear wheels of the vehicle. Use approved chocks for safety. They wedge beneath the tires keeping the vehicle from accidentally rolling out from under the jack.

Step 3 Place the jack under the lower control arm, as close to the ball joint as possible. This will create pressure against the spring. This is important since the wheels are off the ground, a load needs to be pressuring the ball joint.

Step 4 Jack the vehicle up just high enough to be able to firmly grab under the tire on that side only. The tire shouldn't move because the emergency brake is set.

Step 5 Grab the tire at the top and bottom and rock it back and forth, giving it a good tug each time. Bad wheel bearings will reveal play in the rocking movement.

Step 6 Use a dial indicator to measure bad ball joint wear. Ball joints should be replaced in pairs whether they're both bad or not.

Sourced from ehow.com