I exported the graphics pack from the pure set's *.qst file and imported it into my fresh quest. I tried drawing, the tiles got all weird and stuff and random heart sprites appeared...
Am I doing this right, or do I have to import the set differently/do something else?
just get the quest file and delete everything in it. Same thing is accomplished.
From what I hear, You got combos on layers that are not properly set up now. You must go and re-draw all your screens to fix that. I would suggest not to change the graphics pack in the middle of building a quest because that is exactly what happens.
Also, your heart sprites, You should reapply a clear transparent combo over them and they will be gone.