nothing special, just move the hard drive, install the SSD and then hold the option key at boot to select the hard drive as the boot volume (just to be on the safe side). If you plan on keeping all your music on the mechanical hard drive, then you would open itunes then go to preferences -> advanced -> then change your itunes media folder (the path would be something like: /Volumes/name of your hd/Users/username/Music/iTunes/iTunes Media). Additionally you could use the itunes smart playsists feature to find songs you listen to often, then copy only those songs to your SSD and use two itunes libraries (option key on itunes launch) so that you can get better battery life when listening to music