I am both drunk and 9 hours jet-lagged, so I will revisit this post tomorrow. But the one thing I want to say today -- if the computer with the failing drives is out of warranty, that doesn't necessarily mean the individual parts of warranty (especially if warranty is 1 year only). Open the box, see if you can find the brand on the drives, and look up what the standard warranty for that brand is.

Replacing hard drives shouldn't be too hard ... but it all depends on the brand. One reason we tend to go with Dell is that the things can be generally pretty easily stripped and rebuilt and done other various cruel things to them.