The easiest way is to simply burn a CD from whatever program you use to listen to the protected WMA files and then import that CD into iTunes. The copy protection will be removed and you'll be able to sync to your iPod, iPhone, AppleTV, etc. You could also Google "Protected WMA Files" and find a number of programs (for Windows) which claim to remove the copy protection. But the legality and stability of these programs are probably questionable.

Its annoying when I try to empty my trash can and it wont let me because something ‘is in use’, when nothing is in use. How do I fix this?

While you may not be using it, the system seems to be in some way. Sometimes this happens simply because you've highlighted it and a preview of it is showing in column view or preview mode. If that's the case, click off of it onto another file, then CTRL-click or right-click the file you want to delete and select "Move To Trash". If that doesn't work, usually rebooting will clear the file out of the system. You can also try holding down Option and then emptying the trash.

The new MacBook Pros released in late 2008 are easily upgraded and is user installable. But for older MBPs, the work is a little more intense. As long as you have the work done by an AASP the computer will remain under warranty. The new hard drive itself will have a different warranty and will not be covered by Apple. If you have it done any other way the computer will no longer be covered. For those interested, if you're handy with tools & electronics, it is actually not too difficult. I recently put a 320GB hard drive in my mid-2007 MBP by myself and had no issues.