convert removed internal HDD into external drive

I have a 250 GB HDD that was removed from my MBP and replaced with a 500 GB HDD. I would like to convert it to an external drive that I can access from my computer. (Alternatively, is it possible to replace the optical drive with the 250 GB HDD?) The drive still has stuff stored on it, so I do not want to wipe it clean.

Having never done something like this before, I would be grateful if someone could step me through the process, or point me in the direction of information for doing so. Thanks for any help!

Just buy a USB external enclosure (for 2.5" sata hard disks), drop the HDD inside and your done.

Something like this:
http://www.amazon.com/dp/B002JQNXZC/?tag=macforums0e4-20

I think this will allow you to put the hard drive in the optical drive bay.The page lists the models that it works with. Never used it myself.

Thanks to both of you, mrplow and Slydude! After looking at both options and doing some more research, I am going with an external enclosure. First off, it's much less expensive. I'll wait and maybe replace the optical drive with a new SSD later when they've dropped in price. Also, I found that a second HDD would not be protected with a motion-sensing system as protects the first drive.