Anodized aluminum trim

[Msteel3]

My 1980, 911 targa is near perfect. Original paint and interior looks new. The only flaw is the anodizing on the trim under the rear window is coming off. Left side only. I have a replacement coming. How difficult will it be to replace it? Does the window need to be removed? Could the original be refinished on the vehicle? The car is so clean, I hate to disturb too much if I don't need to.