Repairing/Replacing Rotting Window in Shower

I'm a do-it-yourselfer looking for instruction on how to do a job. My problem is the vinyl window in my shower is trimmed with wood that is rotting. I want to keep the same window but solve my rotting wood problem. I have excluded the idea of a curtain around the window and advanced wood protection. I want to eliminate wood altogether. Also I don't need to use glass block because the window is still good, it's just the trim and surrounding wood and interior that is bad. What are my options and can you point me in the right direction?
All help is appreciated, Doug
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