First of all you will need a Wii compatible SD card that's no larger than 2GB (I recommend getting a 2GB Sandisk from Big W for sub-$20).
I hadn't updated my Wii in AGES so I was able to do the Homebrew Channel install via the Twilight hack. I followed the now pretty outdated guide found here: http://palgn.com.au/viewtopic.php?t=33300 and had to use various other forums to figure what to do with the newer files you need to d/l from the links provided in the guide. If you need any help with this method let me know. :) As far as I'm aware there's not really anything you can do when installing the Homebrew Channel that's going to brick your console, and once it's installed you can update the Wii to the current version without fear of the channel being erased (for now at least).
As long as you don't tinker with WAD files (which I believe tamper with the Wii system settings and are mainly used for naughty reasons anyway) you should be fine.
If your Wii has been updated recently it's apparently a bit trickier and you have to use the 'bannerbomb' method. Don't really know much about this one sorry.