The proper way to replace a sink in a slab counter is to remove the slab and mount the undermount sink to the rough top, then to reinstall the slab. The slab may not survive the removal intact, and whether it breaks or not will depend on 1) weakness of veining, 2) strength of slab adhesive, and 3) skill and strength of the workers.

The shortcut way is to use either a sink designed to mount either top or undermount, such as the Kohler Vault; this gives a very clean look as a top-mount, and a skilled installer could even install it flush by grinding a groove in the slab under the lip of the sink so the stainless sits flush with the counter top.

The easiest but least esthically pleasing way is to use a top-mount sink. Yikes. :)

Retro/Mid-Century Modern has been "in" for a while, but won't always be hip. I'd stick with Italian or colonial, something that's stood the test of time without going horribly out of style. Though if you love Mid-Century Modern and have to have it, go for it!

I am a fabricator.

your only good option is to replace the existing undermount with a drop-in that is a similar size. Creating a new undermount cutout in place is only barely possible and it would be very expensive. However, trimming the existing undermount cutout for a drop-in would be relatively easy. It would still take the fabricator a good hour not counting travel time so you should expect a bill of at least a couple of hundred dollars.

Thanks for the info! I think that unless I can find an exact match, we'll just deal with the current sink until we can renovate. It doesn't seem worth the trouble for something that we'll be replacing in a few years.

David, I'm a huge fan of MCM, and have been since before it got recently popular. An "Italian" or colonial kitchen would look terrible in this house, too - very out of place. We just moved in and plan to stay here for a very long time, so I'm going to do this kitchen for me, exactly like I want it! I don't want to do an exact replica of a 1958 kitchen, but I want to honor the era of the house. The current kitchen has raised panel cabinets and this granite (which, incidentally, I found by googling "cheap granite"):

While there isn't anything wrong with it, it isn't me.

Yillimuh, I love mid-century modern, but it's more recent for me, and will probably pass. If you have loved MCM for so long, it's likely you may continue to love it for the long haul. For me, Danish modern might be my long-term love. :) But there's something to be said for the classical Roman esthetic that has stood the test of time for centuries.

I too want my house to be enjoyable for me, but having seen horribly odd choices in custom homes, I always shoot for broader appeal for resale in my remodeling decisions. But for people who are in homes for the long haul, it makes sense to make it just the way you want it, resale be damned.