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Wood around bathroom basin

The wooden surround of my bathroom basin is rotting at the back of basin & where it joins the wall. See photo. I'm not sure if I want to replace all the wood with say a rimu stained pine & keep the present basin which is in good condition. Or if the back bit can be fixed/replaced. Or just replace the entire basin area. I want to keep the shelving unit at the bottom. I guess I'd like to know how much each option is likely to cost me so I can make a decision asap. At the moment I'm most keen on replacing the wood surrounding entire basin. Hope this makes sense! Cheers.