your best bet is to install bootmii as boot2 and make a copy of your nand this will allow you to restor your system memory incase of a brick. Download it hear
RapidShare: 1-CLICK Web hosting - Easy Filehosting
To install it put the contents on the root of your sd card then click on the little sd card on the main menu and it should pop up saying install boot.elf say yes then follow the onscreen instructions.
hopefully you can install bootmii as boot 2 once this is done shut your wii down then power it back up bootmii should start use the power and reset buttons to navagate through the bootmii menu. scroll all the way to the left then click on that then you will see a picture of a chip with a green arrow clcik on that to make a backup of your nand. once its done copy it to your pc and keep it safe.
Incase of a brick just copy your nand back to your sd card load bootmii up and go the the picture of a chip with a red arrow and restore your nand.
hope this helped