LEH257 as far as I have heard is similar to the LU64 which means they cannot be downgraded. Did you ever have a working Wii at 3.2? Installing preloader on a 3.4 is a recipe for disaster as it's not compatible.
2) You could always try the gamecube mod to see if the recovery ascreen comes up and then worry about using a drivekey. You'll need to change the drivekey autoboot setting on your alternate Wii before installing in your bricked Wii.
3) Bootmii as boot2 would have been handy.
4) A black screen is better than an error screen in this case.
5) Had heard it was just a bit less than a new Wii but it varies on who you ask and where they are sent to for repair.