Hard Drive Connection Issue on MacBook Pro

Hi,

A couple weeks ago my MacBook Pro was running and suddenly went into a non-stop pinwheel freeze. After waiting a few minutes I decided to do a manual shut down and when I attempted to reboot it, I just got a blank white screen that wouldn't go away and then a blinking question mark folder when I tried it again. Luckily I already had an external HardDrive Dock so I removed my Hard Drive, used the system startup Disc that came with the computer to redirect the start up disc, and I've been able to boot my MacBook from the Dock since then through a USB cable. So I have a temporary fix, but of course it requires a lot of set up, it's a slower connection, and is less convenient when I take my laptop from place to place.

What I want to do is replace the connection between the Hard Drive and I my MacBook but I want to make sure that I purchase the right part. My MacBook is two or three years old now but it runs fine (besides these issues) and is fast enough for all of my needs. My Macbook is a MacBookPro5,5 with an Intel Core 2. I believe it is a 15 inch model. I'd like to avoid taking this to the Apple Store if possible because I have a limited budget and this should be a pretty simple repair as long as I'm replacing the right part. Can anyone tell me what the probable part is that I need to replace?

Thanks,

Todd