It wasn't really a problem, more of an upgrade. So I have a Mac Mini Server and a 13" Mac Book Pro. I find that I barely use the optical drive in my Mac Book Pro and decided to take it out and install a 500 GB HD from my Mac Mini Server in place of the optical drive by using the Optical Bay I got from ifixit. I noticed that the boot time for the Mac Book Pro got a little longer when I upgraded to Lion so I purchased a solid state drive and swapped it out with the boot drive. Now the Mac Book Pro boots up in like 3 seconds. The 320 GB boot drive from the Mac Book Pro is now the Boot drive for my Mini Server while using the second 500 GB drive as storage.
The swapping process took awhile but with the help of ifixit, it went pretty smoothly. I used the Mac Mini Hard Drive Replacement guide and Macbook Pro Optical Drive Replacement guide to help me out. The 26 Piece Bit Driver Kit that I got from ifixit was very helpful.
My advice is, take your time, there are a lot of small screws in both of these machines. If you do things too quickly you may end up losing some of them. And make sure you read over the repair guides once before starting the projects. And since both my laptop and desktop were down I couldn't use the guides online. Another recommendation is print the guides for reference.