I am quite new to pc recording through devices. I recently bought a Line 6 GX and got its software (PodFarm, RiffWorks and Ableton). I appreciate all of them, but I find Ableton most suited to my needs. The problem is that I want to introduce drum loops into it--particularly from RiffWorks--but I do not know how.

Also, when it comes to final mixing, why does the volume suddenly drop when I convert from .wav to .mp3?