If it's just a bent pin, you can actually fix it without opening the system. Just use something small like an IC extractor or a small set of tweezers to straighten out the pin.
If there's a missing pin, then you'd have to open the system casing and inspect the severity of the pin breakage. Go to radio shack and buy a simple D-sub connector and pull one of the pins out from it to use as a replacement. You'll have to solder it to original pin wire that attaches to the motherboard, so depending on how skilled you are at soldering, you may or may not want to attempt this on your own. Ask around...Jeff Kurtz or members like broken may be able to help you if you need it. If you want, I can always take a look at it and try to fix it for you, but you have to make the decision as to whether this system is worth your time and money or opt to go with a fully working system if this is too much of a hassle for you to go through with.