Well, how did he brick it should be the thing you should say it. What process did he do to brick the console?
I'll give a few starters for what you can do with certain bricks. Be sure of what type of brick it is before proceeding.
Did he install a WAD file and brick it? If so, it's a banner brick, and all you need to do is un-install that WAD. Boot into BootMii, go to the Homebrew Channel, and use WAD Manager to remove the WAD file.
Did he remove a system menu IOS (really dumb thing to do, don't know why someone would do that in the first place)? Run a syscheck, post what IOS you have on the console on here. We can identify what is missing if you cannot figure it out yourself. Then, use ModMii to download the missing IOS file and install it onto your Wii.