Not him, but it's actually pretty easy to do.
First, you need to have Wario World visible in your games library in Dolphin, via making sure the Paths section of Config is pointing to where the ISO is. Then, right-click it, pick "Properties", and look through the tabs on the top of the window that pops up and find "Filesystem". From there, right click "Disc - GWWE01" and pick "Extract Entire Disc", and have it put it somewhere you can access easily.
Next, go into the folder this made with the game's unpacked files and look for the "main.dol", should be pretty visible and easy to find. Overwrite that file with the one from this page, and now the game is modded. Don't move or mess with anything else, just leave it all as-is besides that .dol file.
Last bit you need to do is repack it, which is also very easy. Either stick the folder full of the unpacked files that Dolphin made into the folder where you've already told it to find your games, or add the path for the folder manually to its list. You should see another copy of Wario World pop up, you'll be able to tell it's the unpacked one by looking at things like filesize, although you can also make it easier by just temporarily moving the original Wario World ISO somewhere else instead. Right-click this new Wario World, and hit "Convert File", then hit OK with the default settings, which will pack it into an ISO file.
Let it finish that up, and you're all done, with a crisp new ISO that is modded for co-op shenanigans. Make sure to rename it in explorer so you can tell it apart from the regular copy when browsing files, as well.