Definitely worth cleaning up, just make sure you do a thorough job with lemon juice and then clean (again thoroughly) with IPA. It may need some repair work to traces, depends how much the corrosion has spread but if you're lucky it might just be on the surface.
If it does end up as a problem to get it working as above the parts on the board (especially the 2mb Agnus) are quite valuable and you could even get it transplanted to an A500++ board
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