Yes we are or should be going for นิพพาน. But นิพพาน is NOT end of life.นิพพาน is about freedom from cycles of 'defilements' (in particular lobha, dosa, moha or tanha).

I think the talks of previous-life kamma are from outside Buddhist teaching. The Buddha says 'we are the owner/maker of kamma and heir/receiver of kamma'. And we can live life that lead to freedom from 'bad' kamma.