Usually you can replace the steering coupling before the box. Try that and see if it helps. It's been known to be a cause of steering play. I think the coupling is about $35 or so. Although I must say, a new box makes the car so much nicer to drive. Like a brand new car! I did a new box in my '80 300SD and boy did it make a difference! I am currently putting one in my '77 450SL. The old box lasted for 167K, not too bad by any standards.
'67 250SE Cabriolet
'93 300E 2.8