Hey everyone,
since I've bought my Nintendo Wii console in September 2008 I didn't have any problems so far.
But, a few days ago I bought Nintendo's newest highlight game "New Super Mario Bros. Wii";
my Wii now states that it required an update to proceed, furtherly that any modifications could cause damage to it. (Yes, my Wii has a Wasabi modchip, though I don't know which one exactly)

Naturally I didn't proceed. Next thing I did was calling the shop I'd bought my Wii from to tell them the problem.
All they stated was 'You may proceed, if you don't have anything additionally installed.'
I responded that I have installed the Homebrew channel and some virtual console stuff.
He then eventually stated that I am to remove those things first before updating the Wii.

So to cut the long story short: How do I completely remove the things I installed then, to be insured that nothing is going to happen to my Wii if I update it?
I'm asking because I think somebody once told me there was a special way one should use to definitely completely remove those modifications.

If you need any further information go ahead and ask; PLEASE help me