It appears that you have a 2cm top with a 3/4" plywood underlayment supporting the sink. Under no circumstances do you want to attempt to pull the top, so the sink has to come out the cabinet front. Ripping through the sink and top for a top mount installation will be a nightmare.

Remove the doors/drawers and after removing the screws to adjacent cabinets, place a wood block on the back of the cabinet front. Smack the wood block with a hammer until you drive the cabinet front off. You've to to get access to that plywood. You may have to pull your dishwasher, but you've got to cut the plywood to free the sink. This isn't going to be easy or fun, but it's the only way, I promise. It may be easier to cut the top of the cabinet sides. I know it sounds crazy and radical, but the cabinet sides are easily hot melt glued back in place.

I'd use a multi tool to cut the plywood. Cut the front and sides, then drive the sink out from under the rear plywood with a rubber mallet. Cutting the rear plywood is much easier when the sink is gone.

Now that you've got the sink out, you'd be crazy to not undermount the new sink. Hot melt the cabinet sides back in place; screws and cleats wouldn't hurt, clean the stone bottom and the sink flange, install a Hercules Universal Sink Harness (BB Industries), place the sink in the cabinet, hot melt the front back on, silicone the sink flange, run a bar clamp through the the drain hole to a 2x spanning the sink, tighten, check your reveal, tighten the HUSH, pull the clamp, check the reveal again, adjust if necessary, Windex the silicone squeeze out, and you're done.

Thanks much for your response, Joseph. The thing is, we know this guy who will cut the sink out. That will not be a problem. What I am concerned about is hanging that new 50 pound sink Over the granite overhang. Is that advisable?

"That will not be a problem." Really? lol. You have been warned.

It'll take a diamond blade to cut through that sink. While that diamond blade will make short work of the cast iron, the plywood will give that diamond blade hot smokin' fits. Open all your doors and windows please.

To answer your question, the granite will easily support the sink, however, installing the manufacturer-supplied clips to pull the sink flange to the top will be difficult to impossible to install with the remaining sink flange still in place. If you pull the remaining sink flange, you may as well undermount the sink.

And no way does the pictured stainless steel sink weigh 50 lbs. 5 maybe.

And when he gets frustrated and wants to take a sledgehammer to the sink, show him these please:

And that was with NO plywood.

So you do not advise cutting it out. Hmm. It’s been really hard finding anyone willing to spend that effort here unfortunately. They are all pointing us to the granite guys. We are almost thinking of returning the sink now. Let’s see what happens. I will show him this post and hope he is willing to go that way. Thanks much!

This one does weigh a lot!

I stand corrected. Apparently it does weigh 50lbs.

I do not advise cutting it out. The granite guys are interested in selling you new granite, not in replacing this sink. They will offer a free sink that they paid about $20.00 for, but with as cheaply as some of them work, that may be a cost effective option.

I don't see how returning the sink is an option. When you go to sell your home, the buyer is going to take the cost of the sink/granite replacement off the price, so you are going to pay now or at closing. If you pay to fix it now, you get to enjoy the new sink. If you wait until you sell your home, you'll buy a sink for strangers that you never got to use.

Lol, Not selling soon...moved in like a year ago. We really want this sink, but it just feels too heavy to go on the granite overhang. Not sure it’s worth the risk. Might swap it out for a less heavy one.

Komal:

The stone will easily support the weight of that sink, I promise. There is virtually no risk and absolutely no risk whatsoever if you undermount the sink.