As John says "does this happen with any of your other lenses"?
As for MA-ing your lens this is very simple, download a focus test chart.
http://www.dphotojournal.com/downloa...us-test-chart/
however this will only adjust the camera/lens for front or back focus.
I guess you need to check whether indeed this is front/back focussing.
I assume you have switched to manual focus and used Liveview at full 10x magnification, if only as a test.
Harry