(sorry this sounds like Spam but I'm not with Lowes!) Below is a link to Lowes moving discount coupon. I got 10% off up to $5,000 in one shopping trip. I went to Lowes a few times to tally up everything I needed than bought it all at once. I believe there are stock items of popular Kohler (and others) sinks and faucets with excellent pricing, then you get this extra 10% and don't have to pay shipping. You do have to go get your orders when they come in. This way I got at Lowes (but you could at Home Depot too) towel racks, TP holder, Vanity hardware, faucet, sink, glass shower door, Swanstone tub surround, light switches. Here is a link that might be useful: moving discount 10 per cent coupon

The undermount sink should have been attached to the counter with a bead of silicone and cleats that screw into a depression on the underside of the counter. Faucet location has no effect on this. If it was installed correctly, you'll have no issue replacing it. If it was installed differently, you might have a problem changing sinks, and may want to have your sink repaired instead. You'll have to have a plumber take a look and give you an estimate. By quartz, you mean the manufactured acrylic and stone chip counter, correct? These are a little more rigid and tougher to repair (should there be a crack) than solid surface acrylic counters, but again, as long as the sink was installed properly your counter should be just fine. I've found both Ebay and Amazon.com to be good sources for sinks and plumbing supplies in general. If you're going to choose a stainless steel sink, go for the lower guage (16 vs. 18) if you can afford it, and check out the SS sink thread (below) from a week or so ago on this forum. I have never understood why anyone with a dishwasher would want a two bowl sink, so as far as your sister's comment, it's a little outdated. In the olden days these were useful for washing dishes on one side and rinsing on the other. Today we tend to use sinks for food prep and disposal before loading the dw. Two smaller compartments make the sink less useable: which side gets the garbage disposal? How do you wash large roasting pan with that wall in the middle of your sink? I'm sure you will find the single bowl much more useful. I doubt either will have much effect on resale. Here is a link that might be useful: Stainless

Not what you asked, but are you sure you need an air gap? Are you in California? Your name doesn't indicate that. I think California is the only state left that requires an air gap (maybe Maine too). That's because dishwashers today come with a "high loop" hose installed, so that you don't need an air gap. If your name means you are in Wisconsin, Wisconsin does not require an air gap. Please refer your plumber to WI Code which describes the requirements for a "below-counter air gap", i.e. a high loop installation on your DW. If you are in California, what many people in California do is have the air gap installed for the inspection (if you are having one), and then replace the air gap with a soap dispenser. If you decide to do that, you won't need 3 holes, just 2. For spacing, my single-hole faucet is centered over the sink, and my soap dispenser in on the right, 8" on center from the faucet center. Standard hole size for faucets is 1-3/8". I'd actually never heard there were different hole sizes than that.

Some bathroom wholesale shops sell inexpensive oval white under mounts for like $50. Might want to try that. I would make a template of the hole you have and take that with me to make sure.