Sad day for HP-41C

[d b]

I'd soak it in vinegar first to neutralize
the gunk. then rinse it a few times in distilled water and let it dry a few days. An unlit oven warmed with a pilot light or a south facing windowsill in the winter will help that along. Proceed how you see fit once you can tell what your traces look like. I have used a paint-on nickel solution to restore conductivity. A long time member here, Diego Diaz, made some battery blocks and he still might have one. You can PM him.
You'll probably get more complete instructions as people find this and comment. Good luck.