Since it says for downgrading from a 4.0 Wii and yours is a 3.4 then personally I would not use that guide. I suggest you look at this one
[Only Registered Users Can See Links. Click Here To Register] and see what you think as it is for Wii 's using 3.1 - 3.4 and is written by Dogeggs so should be fool proof. Also worth reading through the posts to it if you run into an issue as it might already have been answered.