190E sloppy steering question

I have a 1985 190E 2.3 with 168,000 miles on it.
The steering has felt a little loose for a while but I just put new
tires on it and now it is impossible to drive on the hiway.
It jumps right and left like there is a huge amount of play in the steering.
My question is this, I understand that the steering box is adjustable to take play out of the steering but there is no instructions in my Chilton manual, can someone explain how I would do this??
Question 2, how hard is it to rebuild the idler arm, I'm guessing that by now it needs a rebuild!!

Thanks in advace for any suggestions!!

Craig