Both Hard drives failing on Power mac G4 MDD

I have this Power mac G4 MDD (I think it's 867ghz) with 2 hard drives (60GB and 40GB). About a year ago the machine started making a constant clicking noise like a very loud clock. Recently I noticed my 40GB drive was not on the desktop, couldn't be found in any search and couldn't be retrieved with any apps I tried. I did some searching online and found a SMART utility and tested the remaining 60GB drive and it is reportedly FAILING.

My question is, would replacing the hard drive(s) with a working hard drive make this a viable machine? Is the clicking noise related to the failing hard drives or is it a completely different issue -- motherboard, etc.?

Thanks!
Marjorie