Yeah, this really is a nostalga trip for us too, though this is a lot more slick than the first MKWii texture hacks. The replacement is done by editting the .bfres file for the track on our computer, along with swapping the .bgenv file in from another track to generate the night time post effect, and editting the course's .byaml file to remove the plants and bird's nests as well as turning on the headlights, turnning off the pollen and changing the skybox. The edits are then loaded in with our Riifs-like network file loader, so when the game asks for each of the files, we stream it over the network instead. What the video doesn't show is that this increases the load time to over a minute! We'll have to look into making an SD or USB based patcher at some point down the line to try to increase the speed. 1mbps over the network just isn't enough anymore!
Damn, that's a lot more impressive than I thought. Nice work!
How were you able to gather information on the file types so fast? Also, I'm excited to see that it's apparently a similar file format to the previous generation!