Well your choices are limited within the series of your system. So if we look at this listing: MacBookPro5,1 Series. These are the ones you can swap parts around with.
The fact you are able to get the system to boot up at all may not be as bad as needing a new logic board!
Are you up to working on your system? Do you have the needed tools and work area? You'll need an ESD mat and wrist strap as you will likely need to take the logic board out to clean it.
What I suspect here is the HD controller logic, cable or HD is not able to communicate so it has to re-try a lot to get the data in or out of the systems logic board. So what we need to do here is clean things up and see where things are.
You'll need some distilled water (not tap!), Isopropyl alcohol 85% or better, cotton swabs (Q-Tips), a soft paint brush and toothbrush, and lastly, a can or two of can'ed air.
What you'll need to do is take your system apart so you can identify what areas need cleaning
Use the soft brush and can'ed air to clean off the loose dust buildup.
Then using the swabs with the distilled water wash down the areas being careful not to pull anything off when there is discoloration or clear spillage.
If needed use the tooth brush but be very careful with it as it an be to aggressive.
After you clean off the areas go over it again with some fresh distilled water and lastly go over it again this time with the Isopropyl alcohol which will help remove any oils and act as a drier to help remove the distilled water.
Use the can'ed air again to blow out any wetness. Let the parts dry a good day in the warm sun. If you see any part that can't be cleaned you'll need to replace it., that may include the HD.
Let us know how it goes! Good Luck