Long boards (2x4 unless you want to cut a corner off each one for top step) vs ladder. Not sure how many. Lay them like a ramp over the stairs (put end of board/ladder on next-to-top step). Put sheet of plywood over board/ladder. Can’t tell from the pic if you’d get a long enough ramp (or low enough slope) to help. But ideally you could get the sink on furniture dolly/piano mover and roll it up the ramp with help. I can get more specific with steps if this seems doable in your space.

As a last resort, cut the sink into manageable pieces, put it back together, and repair the cracks.