If you have your stuff backed up, like rman says, your best bet is a new HDD, I just picked a brand new 250 GB laptop HDD for £80 GBP, and then somewhere in this forum is a method for swapping out your hard drive, works a treat
If not, it may be possible to recover the data professionally, but it may cost you. If the mac is still within warranty or you have procare you might be able to sort it on that.
Hope you get it fixed
Dave