Upgrading iTunes Artwork


I want to upgrade the quality of some of the cd artwork in my iTunes library but I cannot delete the old artwork without deleting all of the music tracks as well. How do I delete the existing artwork (not the music) so I can import (click and drag) better quality artwork in.
puerto
OK,
Going to just tag this on as I am trying to find all the album covers. Best sites to get artwork from? Would love to hear where everybody get artwork from. Or how they use goggle for this, never done it that way

Inwanw
Inwanw,

To google artwork:

Open browser, type google.com in address field, click "images" link at top left corner, type in album title in search field, click "search images" button, select the image that matches your album and looks best to you.
Thanks to all for the instruction: It works! Inwanw: I use two sources for the artwork: Amazon Music and seekacover.com. Both seem to have good quality stuff. If I'm not totally happy with one image I switch to the other site for comparison. That's it though, I'm not one to roam all over the place. Again, thanks to each of you.

As a side note, last night after getting the advice from Sidssp I started working up the updates and 10 albums into the project the darn wireless router went out on me. I'm just now (1:00 PM) the next day getting back into it. Aarrggghh!
OK Folks I want to thank you all. I have now manged to get all the artwork correct. And I still cannot believe that I did not see the images box in goggle.
inwanw
inwanw: Glad it worked for you. My library is looking much better also thanks to the responses on this thread.