the plumbing will need to be detached. Depending on how the faucet was installed, this could be a 10-minute task or less. The sink may take more effort depending on how it was attached. I just looked at your pictures. That's a nice sink. It will take a few minutes to detach the disposal. If he used standard attachment clips for the sink, it won't take long to get off. The only 'issue' will be the silicon sealant which will take a bit of care to separate so as to not scratch the sink.

I have a light countertop with my wood cabinet, but with your backsplash I think the darker one would look very nice. Sometime the backsplash will get damaged when removing the countertop or the new countertop is a different thickness causing a gap. Be sure to discuss this with your countertop person. You will have more options if you change the backsplash too, but there is no need to if your countertop place can make the present one work.

@kel_kat5 - It is a mistake to think that Dayana’s situation is representative of granite counters. Most importantly, the Bahamas White granite she pictured looks like it’s in the family of the Imperial White or Kashmir granites, which is notorious for behaving more like marble and staining easily because it is more absorptive than other granites, I.e. porous. If one is looking for a granite with a white background, check out the granites in the family of Alaska White, White Springs, Bianco Delicatus, and Lennon, which are pretty bullet-proof. I’ve had different granites in different homes, and none even needed sealing, and were carefree, and we didn’t baby them. There are a thousand granites out there, and they should not all be lumped under the same umbrella. Quartz is a great choice if you want a more uniform appearance to your counters. There are stories on this forum of Quartz staining, scorching and chipping, and having resin pools. I actually think Quartz is a wonderful choice for counters. But get it for its appearance and beauty, not because you think it is more durable than granite.

Google some poultices please. It's trial and error. Good luck.