If there are no nonland cards remaining in your library, you just randomize your library and continue playing.

You can't pay and not sacrifice a nonland permanent, or vice versa. The cost must be paid in full or not at all.

While resolving Dreamshaper Shaman's ability, you can't pay more than once or sacrifice multiple permanents.

Dreamshaper Shaman can be sacrificed to pay for the cost of its own triggered ability.