As long as you don't touch or make any changes to the old drive you should be fine. Just image backup the old drive, replace drives and restore to the new drive. This way if there is any problem, just put back the old drive in the laptop and restart - you should be back to the current status.
As for mounting a hard drive, you can do that using the 'mount' command (this would last only until the next log off):
In the following example the drive partition /dev/sda2 was mounted to the folder /home/david/newdrive. You have to make sure that the destination folder exists:
mount <device name> <mount point>
so now the folder /home/david/newdrive IS the entire drive partition /dev/sda2
mount /dev/sda2 /home/david/newdrive
To make the mounting in this example persistent between reboots, edit (CAREFULY) the file /etc/fstab to add the line:
Of course, change the 'ntfs' in the line to the correct method.
/dev/sda2 /home/david/newdive ntfs 0 0
You can find more info about how to edit the content of /etc/fstab at: https://help.ubuntu.com/community/Fstab
Hope that helps.