if you want to update your wii w/o requiring certain disc i would only update to 4.0 or 4.1 and use bannerbomb if you update past these system menu you will have to aquire one of 4 games to softmod your wii where as bannerbomb can be done by dragging files to and from your sd card alot easier. But yes ModMii is the best way to go about soft modding your wii

not sure if you can use bannerbomb on your 3.2 wii but not needed if you have the hbc anyways. Updating your system menu by either Wad or Safe Installer will not erase your softmod.
You should also note forwarder channels cannot be deleted by system menu updates (offical) from what i've read and there by you may want to install a forwarder channel for one of you wad manager (MMM is a good choice or YAWM). While your at it grab IOS236 installer app and install that so just in case something goes wrong you still have access to wad manager

and IOS236 will have all permissions needed to install anything.
ModMii --> http://tiny.cc/ModMii
MMM --> http://tiny.cc/MultiModManager
IOS236 installer --> http://tiny.cc/cios236
Basically what you probably did was patch IOS36 to get homebrew working since you did it so long ago and what IOS236 is just a patched IOS36 installed into another slot like 236. So a freak official update by a family member wont render you helpless so you can reinstall everything back to normal.
Take the advice given above and rehack your wii however i wouldn't say formatte your wii either just reinstall everything. Also now im thinking of it if your on that low of a system menu you have to have bootmii? full brick protection so if you do mess anything up as long as you have nand backup of your console your good
if your simply just wanting to not be bothered with updates install Priiloader --> http://tiny.cc/Prii6f and get the hash file here --> http://tiny.cc/PriiHashHacks and disable disc updates and your super mario bro's will not bother asking you
So in the end you do not need to redo your soft mod unless you would like to. I would just to know i have the latest but it's your choice

Remeber Priiloader and Bootmii go together like Butter Toast mmmm ;-p