This is a quick response to acknowledge your message and provide some basic information. The next time I will be able to access my records is Saturday so for now I will provide some comments from memory of the replacement which was now more than 100,000 miles ago on my 1999 E300 Turbodiesel. The replacement was done as part of a full front suspension rebuild at about 172,000 miles. The car now has 287,000 miles. Since the full rebuild was done, I have again replaced the lower ball joints and stabilizer bar end links.

You mentioned the left upper control arm which to me means the left side as one sits in the car looking forward. This is also the side with the upper control arm that is easier to replace. You will need the upper control arm which comes with a new upper ball joint pre-installed. It is also recommended in the MB WIS that you get a new bolt and self-locking nut.

The head of the bolt and the nut on your existing upper control arm are accessed through the engine compartment. The approximate location will be obvious when you see on the new control arm where the long bolt fits through the arm. Once I had the car safely supported by sturdy jackstands, I removed the front wheel and removed the very heavy spring that goes between the lower control arm and the spring perch. This was done with a
W210 model-specific rented spring compressor tool (available for rental on the tool rental forum of this Peach Parts site). I do not remember if the spring removal is necessary if you are only changing the upper control arm but I did remove it because of the complete front suspension rebuild work I was doing. Removal of the spring is potentially VERY hazardous if not done properly or if attempted with an improper or defective tool.

You will also need a ball joint separation tool. These are also available in the Peach Parts tool rental program or possibly at your local auto parts store in their rental program.

After you install the new control arm, the long through bolt and nut must be torqued to a specific value. I believe the torque must be set when the weight of the car is on the wheels with the suspension in its natural at-rest state. The nut that attaches to the upper ball joint stud also has a specific torque value. As I recall, the torque values may have been posted in an earlier thread about this type of repair job. When you are done with the replacement and all is back together the car will need a front wheel alignment since the work you just completed changed the alignment settings on the left side.

All of the above comments and information are intended to be of assistance to you. I am not a certified mechanic and assume no liability for anything related to repair of your vehicle. This is all in the spirit of sharing my own personal experience with this repair that may or may not be similar to yours.

Others on this forum may have more recent experience doing this repair and have access to the correct part numbers, torque values and WIS files.
Hope this is helpful to you.
Ken

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2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)