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Firstly, you posted both of your threads in the MAC PRO forum-for Apple desktop computers. I moved both to the appropriate, "Mac Notebooks" forum.
Second, the notebook forum moderator copied your first thread into the inclusive "water spill" thread-and then answered your question about swapping out the hard drive. I agree completely with his statement that it's unlikely anything happened to the hard drive in the damaged computer.
Finally, you can simply check the part numbers of the two computers to see if they're similar, but if they are basically the same model and that close together in age, the hard drives should be completely interchangeable.