1 - 2 hours
A friends iMac's hard drive died, all their family photos and business data was on it. No backup (I know, shame on them). The iFixIt site gave me the information to replace their hard drive. My handy Linux box gave me the tools (testdisk) to work around the failed hard drive and recover their data. Success!
Great. The online guide showed exactly what I needed to do.
Backup your data on a regular basis!