How tough are these lenses?

[Swimmer]

I had my 30D on a tripod with a Tamron 2.8 28-75 lens and plastic diffuser on it. The tripod had only one segment of leg(s) extended so it was only about a foot or so off the hardwood floor. Anyway my crazy little nephew must have gotten to it when no one was around. I found the camera on the floor with the plastic diffuser broken. I don't think he pounded on it or anything...more likely just tipped it over. Since then, my shots don't seem to be quite as sharp -- though I'm not sure that's not just me being paranoid. I also noticed that I could wiggle the very end of the lens a little bit (maybe a quarter of a millimeter?) -- not sure if it was that way before the accident. Everything else seems to operate as before.

Also, what is a logical range of cost for having Tamron calibrate or repair this lens?

[Dbl]

I have that lens as well, they are fairly robust. Based on what you can buy one for it might not pay to send it to Tamron for repair. You also would likely be without the lens for 6 weeks or so. You might try Marquette Camera Repair and see if they would give it a check, I would think for considerably less than the factory. I am always paranoid myself and rest easier when things are checked.