You should ALWAYS clean install when switching ROM's; this means nothing will hold over. When using a TouchWiz (stock) based ROM, there are no assert lines, those only exist in AOSP based ROM's like Cyanogen, Carbon, CyanFox, etc. Therefore, after a clean wipe, flash the ROM and then flash your preferred APN fix in the same session, then boot back into system. Both Wicked and MOAR take a very long time on first boot, and there is a lot to set up in general, so be patient.
Wicked Sensations v. 0.4 XDA Thread
MOAR 8.0 XDA Thread
Don't forget to leave a "Thanks" for both Dazed (Wicked) and Rompnit (MOAR) as they are both huge assets to the SGS3 community and just plain awesome guys!!