The granite has to come out first. Figuring that the bottom of the sink slopes down to the drain some amount greater than zero. The sink is effectively taller than your space at the drain flange. To slide the sink directly in place you have a tolerance of zero with the granite tops in place. Something's gotta give.
Casey

thanks, casey. instead of moving the marble, can we clear enough space underneath? we have now managed to get the old sink out this way -- but we are nervous about getting the new one in.

OK,
You got past my first area of concern; now the issue will be will the scribing done for the old sink accommodate the replacement? Will it gap unacceptably, or will the new one be too tight to go?
Casey

That is exactly what we are concerned about. The new sink should be here in a day or so. We are hoping it will be a bit bigger than the old one but if it is smaller we will have a gap. If that happens we may need to find another piece of gumwood and re-make the front panel-- we really do not want to have to do this. But we recognize we may have to. We are getting this gumwood from the center panels of old doors that we buy at salvage. We learned the hard way that it is the only way to match the old gumwood that is already in the kitchen. The front panel that is under the sink is contiguous with the two stiles that run down on either side of the two doors in the cabinet below the sink. My DH took such pains to craft it and we are sick about the possibility of it not fitting the new sink.