Mushrooms at the base of my Japanese Maple: Is it done for?

Not a good sign in that mushrooms do grow on non-living (dead) organic matter but just maybe it is growing in dead separating bark and the underlying tissue is OK? You can call a certified arborist out to look at it to give you an assessment.

Those are not chanterelles! Do not eat them.

My best guess is poisonous jack o lantern mushrooms. They grow on dead wood but can grow from dead wood attached to otherwise healthy trees.

Good chance your maple is just fine.
Some info here