Gameboy Pocket corrosion, what to do

Recently bought this Gameboy Pocket and at first glance I saw nothing wrong except for some cosmetic shell damage. Upon opening it up I first noticed the rusted screws and was then greeted with the crumbling silk screen (?) underneath the d-pad. The pictures make it seem a lot worse than it does to the naked eye. Some vias are slightly corroded. If I look real close at the battery terminals I can spot some light (left over?) corrosion. I suspect it may have been cleaned before because the button membranes are spotless. Functionally everything works as far as I can tell, except I haven't tested the dc/audio jack but I don't really care about those.

What is my best course of action here?

Thanks in advance!