Changing iTunes file designation frustration

I bought a new 500 GB hard drive upgrading from my 250GB drive around the New Year. I have been putting all my new music and media onto the new hard drive, but have been hesitant (and too busy) to clear my iTunes and re-add my music (which remains the same, plus some new additional stuff). Is there any way I can just change the directory/file destination in one quick go without breaking all the links, album artwork and organization I have done to my iTunes? I hate running essentially three drives [250, computers 250, 500] at once, and I want to just have my iTunes running off the 500. Any help would be greatly appreciated.