debrak2008, I have to figure out how to post a pic here first :P. But the countertop is those yellowish cultured marble top (you see a lot of those in the older houses) but it's not one-piece. The sink is an undermount sink, so it's just like the typical granite top with undermount sink you see now. BUT mine is not granite top obviously, and the sink is rusty and scratched. sjhockeyfan and weedyacres, Thanks for your link! Yes I looked on craigslist and saw some ads for prefab granite tops too. And my friend told me about this too. But my problem is I can't find my size, esp. the 72 inch SINGLE sink countertop... :(. And if I custom made that one, it's expensive. The worst is that I need one 60 inch (I found that this countertop is the only one that's the most typical size) and one 72 inch that's matching right, cuz they're in the same jack & jill bathroom! For the 36 inch countertop for the half bath, the problem is the depth is 1 inch more shallow than the typical tops, so it's 20 inch. And I can't go any deeper because the top is right next to the door opening so 21" countertop won't work! So yes, my house has some strange bathrooms and I figured either we spent more money to hire someone to renovate (but we don't have that funds now) the bathrooms, or we try to make small changes. Of course, I wish I could be as handy as most of the members here then the problem can be solved easily :( Anyways, thanks for all your answers! Please do share if you have any more insights. Thanks again!

Thanks, Vith. The goal is to gain counter space to one side of the existing sink cabinet, and I thought we might gain enough by shifting the sink cabinet as far to one side as the existing plumbing (inflows) allows. We may end up moving plumbing anyway, but we're on a tight budget so I was looking at less costly options. But if I understand correctly, you're saying the drain could still be in the center of the sink; is that right? I like the fact that an offset drain allows you to empty the strainer without removing, say, a large baking sheet from the sink, so I may opt for the offset drain anyway. I thought it might also simplify the under-sink plumbing as well.

"Would they need to remove the current corian, take it to their shop to work on it, and then replace it?" Some like to do it that way, I don't. The cost depends on the sink you choose as a replacement. I'd pull that sink, profile and polish the edge, undermount a nice Kohler 22"x33" Vault, and reconnect the plumbing for $500.00-$900.00. Here's that job in stone, but you get the idea: If you are willing to sacrifice your backsplash to give me some matching repair material, you can have nearly any sink you please. I strongly recommend the seamed undermounted Edge series from Karran, stainless or silegranite. You need to be comfortable in the $1,300.00 range. Before.After. This billed at $1,400.00 not including the sink.

"Hello! Is it possible to replace my current sink with a single basin sink without taking off the granite counter top?" Yes. I've done it a hundred times and haven't ever pulled a top to do so. "My sink an undermount that I assume is glued to the bottom of the granite?" It may be "glued", but is more likely siliconed. Simply release any mechanical fasteners, disconnect the plumbing, then drive a stiff scraper between the bottom of the stone and the sink flange. That thing's coming out, believe me. "Granite sink opening measures 28.5" by 15.5"." I suggest the 3118 from MRDirect. You'll have about a 1/2" negative reveal (the top will overhang the sink) and the corner radii may not match perfectly. I've used this sink many times in this application. Your sink will come out of and the new sink will dunk into your existing cutout. "If this IS possible, what type of contractor person do I contact? Or should we try to DIY it?" Some plumbers will take this on. You don't say your level of DIY skill. If you're moderately skilled and experienced, you shouldn't have much trouble. My last one took me two hours complete. Use the pipe-clamp-through-the-drain-and-2x4 method shown here, please. You'll also want to install the sink with (2) Sink Straps from Regent Stone Products. No clips, please. Side to side, behind and in front of the drain. Same sinks, nearly the same cutout, before and after: