I already tried the MIOS hack mentioned on
http://wiibrew.org/wiki/Wii_Gamecube_Homebrew_LauncherWhile it boots my Action Replay DOL fine and Gecko OS 1.06 Gamecube.. unfortunately it renders the DVD drive useless.. otherwise there would already be a tutorial for USB Gecko owners with unmodded Wiis.. but until no.. sorry, guys
Hard ways to do it - all these ways require a USB Gecko so that you can cheat:
1.
-use SD Media Launcher - it should still work on 3.3 (at least it works on my gf's Wii)
-boot Gecko OS with it
2.
-use a new "Works on Wii" Action Replay - these also still work on my gf's Wii
-use its freeloader to boot an old AR
-use the SD Load code with it while having a bootable SD card in an SD Gecko or GC SD reader
-boot Gecko OS
3.
-get yourself old MIOS and BC WADs
-install them with Waninkoko's WAD Manager (installing MIOS and BC is safe - the worst thing happening could be that your Wii doesn't boot GC copies if an installation fails)
-insert an old Action Replay
-use SD Load
-boot Gecko OS
These three ways are verified by me.. all of them work.. though I admit they are "hardcore".