Put one drive in an enclosure and use a program such as the Disk Utility, Carbon Copy Cloner, or SuperDuper to move the existing Mac OS X installation to the desired drive. Alternatively, put the new drive into the computer, connect it to the Internet, start it up with the Command and R keys held down, and reload the OS from the recovery partition on Apple's servers.
Depends on which system your MBP shipped with. If it shipped with anything below 10.7 Lion, you can use the install disks to install that system and then upgrade to ML using your Apple ID.
If it shipped with Lion or ML ...