I got a email from i tunes saying someone signed into my account from overseas. is this a problem

There have been a lot of scam/phishing emails like this lately. You might want to consider changing your password and making sure it is a strong one. You can also add 2 Factor Authentication to your account for more security. If the attempts continue, you might want to consider a name change.

Apple ID has been compromised

 Apple ID Password Change

Note the restrictions in the article.

Apple ID Name Change

 What to do after you change your Apple ID or password - Apple Support     I suggest doing this before you change your Apple ID or password.

 Apple ID -Two-factor authentication

 Two Factor Authentification availability

 Apple ID - Using app-specific passwords

Apple ID - Two Step Verification App Specific Passwords

Apple ID - Two Step Verifications FAQ

if the email addressed you as dear "customer" or "you@your email" etc. it fake

Apple will never address you as anyone except your given name

If you received an email purporting to be from Apple Computer with charges you do not recognize do NOT click on any links or respond to it. See this link to identify an email purporting to be from Apple: https://support.apple.com/en-us/ht204759  See this link to report fraud to Apple: https://www.apple.com/legal/more-resources/phishing/