Curtis and Diana,
Welcome to the Gulf Stream Owners RV Forum!!
I should have welcomed you to the forum on my first response. Sorry about that.
Larry Moore has a good point on both accounts. I am surprised that the warranty company didn't offer to pay only for the sink replacement.
If the sink was installed onto the bottom of the corian or similar material the first time upon manufacture, them it can be replaced with the same sink and not replace the countertop. Of course it probably would have to be removed to do this.
I am sure that it would be available thru your dealer from Gulf Stream.
Gulf Stream ONLY sells parts thru one of their dealers, as most manufacturers do.
Also, If your sink is Corian as ours is in our coach, are you aware that it can be repaired? Corian can be repaired by a good Corian installer that has been trained in the welding of the plastic that the Corian is made of.
I know Gulf Stream also uses a countertop in some of their coach lines that is a laminated material similar to Corian and install a Corian sink that can be replaced but I have never checked the mounting of this sink.
Ron