I agree with Fattyman, Murphy's Law is a Mother and don't mess with Mrs. Murphy!! if you replace one tierod or tierod end, the front end needs aligned. Why pay for an alignment twice to save a few bucks by not replacing both sides. I am in the process of replacing tierods and sway bar links on my '94 S350D. As soon as that's done, it's down to the tire shop for alignment. That is if the radiator shows up and I find the seal driver for the front hub seals before the front end parts show up.
Wayne