is it possible to convert an mp3 or a wav file to it to edit in ModPlug
Modplug loads wave files, not mp3 files. But for editing a mp3 or a wave I suggest using a proper wave editor like audacity or wavosaur.
I opened a wav file in ModPlug but ModPlug loads the pattern with only 1 note at the start of the pattern!!! :'( I need a whole bunch of notes in the pattern, I want to change samples and instruments and stuff... can't do that if the whole song is one sample or note!!!! >:(
How would you imagine the wav file to be split up? You cannot just extract all notes and different instruments from a continuous audio stream, it is a mathematically impossible problem. It's like you want to split up a dish into its original ingredients.
The best way to edit a wave samples in modplug tracker, is to load it up in the sample editor in modplug.