when it says that your disk is damaged.
5 hours for a Permissions Repair would indicate that there is something going on there.
I'm sure the MBP is functioning right now but you may find that it takes longer and longer to start up or to do something.
Start the MBP up using the DVD that came with it and then run Disk Utility from the DVD. Although the abilities of DU is extremely limited, you may get a different answer while booted from an external source.
A replacement hard drive for that machine is relatively cheap and easy to install. See Link:
Once installed, install 10.6 back onto it and then use your Time Machine backup to replace everything back onto your new hard drive.
On completion, upgrade to ML
i tried today to install ML direct online from Apple Store on a MBPro running the latest Snow Leopard 10.6.8. When it demanded the required restart to install the new OS, after a few minutes it reported failure on the grounds my disk was damaged beyond repair.
Check with First Aid reported all OK. Further check of permission said it would take 5 hours to complete which I found exorbitantly long so ended it.
Our 15" MBP seems made in Aug 2009, bought in early 2010 from Apple. Always functioned fine till now and still seems to on SL to which it has returned.