I take it this was on your Mac, correct?
If it was a phishing scheme and caused some malicious piece of software to be downloaded, the (overwhelming) odds are it’s for a Windows PC and won’t harm your computer. That said, you may want to protect yourself from what sounds fishy with a few things.
First off, your suspicions were rightly aroused. Even if it is legitimate, you were right to be worried about it. But you probably shouldn’t have clicked the link.
The first thing to check is whether the link actually goes where it says it goes. Forging a link is ridiculously easy - heck, you can do it right here on the boards at http://www.straightdope.com. If you use Mail, you can see where an actual link goes by hovering the pointer over it without clicking. Or copy the link (right/ctrl-click) and paste into a text program, or view the message raw source.
Secondly, you might want to check that the e-mail was sent from whoever claimed sent it. This is a bit tricky, and unreliable, but you can usually tell if it’s really from the company that sent it. Try comparing the “received” lines with a message that is known to be valid. Look for something like “Received: from cbox-ignite04.apple.com ([22.214.171.124])” and see if the addresses are similar. The problem is that big companies like Apple often change mail servers, and doing the work to find all this out takes a fair amount of time.
The last thing to do is to mistrust messages like this in general. If you get a message from the ITMS, use the channel you normally use to buy or check music (within iTunes). Or if it’s your bank, go to the bank’s website first. If you have questions, don’t reply directly to the e-mail. Find another e-mail address and forward the message to them with your question.