please help! messed up boot sector /dev/sda

hi all:

i was trying to use dd utility copy something to usb drive but accidentally copy the file to /dev/sda (since i don't know which device should be for usb drive under opensuse linux). now i can't boot the machine but i need to recover something important on /home (it is on different slice/partition).

how could i recover it? boot it from dvd?

thanks

_dave