If your password was compromised, LinkedIn will automatically change your password.
Regardless to whether or not your password was one of the ones hacked, it is a good practice to change your passwords periodically. As a point of note, you should not have any two passwords the same AND you should have complex passwords (15 or more characters with upper and lower case as well as numbers and or special characters).
This is a great opportunity for me to plug LastPass.com. LastPass is an online tool (free) which stores all your passwords securely. It can also generate your passwords so every site has a secure and unique password. There are other password utilities out there (RoboForm and others) which are equally as beneficial. I don't make anything if you use LastPass, I just suggest it because it's a very valuable tool for me.