I understand, but it is really easier to hack MKW than SSBB. Maybe you don't want the CTGP way,so I'll teach you another method (Assuming that you use Riivolution):
http://rvlution.net/riivolution/images/2/20/MKWtemplate.xml Go to this page, right click>Save As> Save the XML file in the riivolution folder on your SD.
2. Create a folder called ''mkw''. Now put all your files you want to replace there (you see, you don't need to make any folders, just putting the files in that folder will make Riivolution to patch them in the game
)
3.
http://www.mariokartwii.com/f72/all-mkwii-file-names-list-69522.html Go to this page to rename your files properly according the character and the kart/bike you're going to replace (eg, if you are replacing ''Sonic Bike.SZS'' to Mario's Mach Bike, you will have to rename it ''ma_bike-mr.SZS'')
4. In Riivolution, go to the option ''MKW Replacement'', set it to ''Enable'' and play
If you didn't understand, I'm very sorry, I'm not really good writing tutorials, but I did as best as I could.