you can do this using trucha signer. I reccomend searching the forums/Google for a guide on replacing files. then you take the sound file from the japanese ISO and place it into the english ISO. I have done this myself and I love it, Im sure there are also prepackaged modified ISOs if you look...
I think leaving it at 10 and letting people update themselves if they choose is fine. Ive had problems installing higher than rev10 on virgin Wiis before.
If you run Dop-IOS and then 4.1 Updater will it overwrite the patched IOS60 that you just installed?
IOS-Downgrader is to remove the trucha...
Make sure you have cios before you update. You will need to run IOS-Downgrader to restore the trucha bug. You will need to follow the steps after 4.1 upgrade.
Its technically not necesary but a good idea to restore trucha bugs.
Try clearing your internet settings and then reset them with a static IP and turn Wiiconnect24 on.
You can also use the offline guide to download WADs 1-18 and install those
If that still doesnt work you should be fine with...