You do not mention the mileage that you have on the car or if you have any problems with the suspension/steering or if any of these parts were changed before.
But, what I can tell you from a personal perspective (not technical) is that I recently changed the tires on my 88 190e with 150k miles on it. From what I have read on this forum, the age and mileage of my car made it a prime candidate to get all of this done. The difference is very noticible. I started with the tie rods and the sway bar bushings. Then this past week I noticed that one of the ball joints was bad so I had both replaced. While there, I had the bushings on the control arm replaced also.
If you are looking into this also have the stering dampener (?) checked. What I can tell you is that I now feel that the car is more stable at higher speeds and the feel of the steering is back to what I feel a Mercedes should feel like.
Insanity: doing the same thing over and over again and expecting different results.
2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
1994 - Yamaha WaveRaider (fun to ride)