I am Canadian and currently have an L-1 visa. When I get married do we have to apply for the fiance visa. Will my L-1 visa still be valid or do I have to apply for another work visa?

I don't know details as far as the L1 visa goes. But the K1 (fiancee visa) is for fiancees of USC that currently reside abroad. Are you currently in Canada or the US? I think L1 is company specific right? You can apply for EAD (it's an option) once you file to adjust your status. I personally think it's worth to pay $120 just to have EAD in case something comes up and you can work for any employer. As far I know filing I485 doesn't make H1/L1 invalid.