Lens spanner is less than 30$ at micro-tools. Since you don't have much to lose you can dig into it. Honestly just tightening down the rear retaining ring for the last element is a 2 minute job provided its accessible. If it requires removing the rear cover well that's gonna be more work but it isn't going to require cracking open all the elements or anything.
Originally Posted by newcan1
This lens should be sharp.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.