2005 ML350.
Had a misfire cylinder 1, I swapped over the plugs and wires to cylinder 4 to see if it followed to rule them out, I did put 1 new plug in because AutoZone didn't have the ones I wanted in stock so I had to order them. But one of the ones i had pulled out looked like the previous owner had stripped it and I didn't want to risk putting in back in and not being able to get it out,

It ran worse than it did before, But the misfire moved to Cylinder 4. Moving the wires back to cylinder 1 to see if it was the plugs it started to miss on 1 and 4. Then randomly cylinder 2 started to have a misfire which I hadn't touched.

So, will replacing only 1 plug on a cylinder cause more issues?

Not sure why 3 cylinders are now misfiring, My buddy thinks I need to touch the terminals to reset the computer.