Is it better to bake the pie the evening before serving and swamp it right before serving, or to bake the day before and swamp while it's still hot?

I would do as Amanda notes: prep everything before and bake the day of.

I'd swamp it the day before while it's still hot. Also if you wanted to make it the day of, but make it easier on yourself, then the day before: roll out the dough and line the pie dish; roll out the top layer and keep it on a baking sheet in your fridge; measure out everything for the raspberries. Then the morning of, all you need to do is assemble and bake. Hope you like the pie!