"After you mod your wii, you can 'unmod' it pretty easily by deleting the homebrew channel and anything else you have installed."
This is a pretty dangerous thing to say to someone new. They may just take this as thinking anything they installed they can just uninstall and they'll be fine even if its IOS60 or something that deleting would cause a full unrecoverable brick (without bootmii).
That being said do that first step he said using bannerbomb with the hackmii installer and install everything you can from that. If your wii is old enough to install bootmii to boot2 do that and backup your nand immediately. If you do that that will make removing anything you change to your wii a simple one click process of restoring the nand.bin that you just backed up. (Will revert EVERYTHING back to that point even save files.)
Once you do that, even if you can't install the boot2 bootmii, to start softmodding it just follow the offline guide here:
http://gbatemp.net/index.php?showtopic=144835
You can't do the online guide because you don't have any cIOS installed yet. Since you're already gonna get the HBC through the hackmii installer above, you only need to do steps 1-3, A-B, and 9-10. From that point you can get any backup launchers working as is, and if you want to install the latest cIOS, downgrade and upgrade properly through Waninkoko's updater so you can keep vulnerable IOS's you can just do the online guide from that point on. That being said I suggest you wait whenever there's any official update from Nintendo instead of updating as within a few days there will be safe ways to update posted here most likely.
As for unsoftmodding afterwards without having bootmii installed to boot2, though I would advise against trying to before you know what you're doing, I suggest you keep the .wads of anything you do end up installing such as the ones for any channels or vc/wiiware games. As long as you keep them, you can properly uninstall them through wad manager the same way you installed them as simply deleting them through the system menu won't get rid of their tickets. After removing any of those, you can use IOS and cIOS downgrader to downgrade your firmware to 3.2 and then delete IOS249 (which is your cIOS.) Then do an official update to 4.0 through Nintendo and then run the hackmii installer again and tell it to uninstall everything you installed through it.
Edit: And yea as Fenrir said there really shouldn't be much of a reason to get rid of everything in the first place. Just remember that you NEVER need to delete any IOS that you installed or patched or whatnot, you can always just reinstall a normal version of IOS over it (IOS249 is an exception since thats where your cIOS would install, and even for that you don't REALLY need to delete it unless your Wii absolutely has to be cleared of everything installed on it for some reason. New cIOS versions install over it.)
