The object I want to rotate is a MeshInstance. thanks.
Some resources:
The general thing I am seeing is that is is easiest to just have a node and use Godot's built in transform system handle it for you. So, if you have a mesh instance you want to rotate around a point, a scene tree like this is what you might want:
And then you can move the point around using $point.global_transform.origin = Vector3(1, 1, 1) or similar and then use the normal Spatial functions for rotating, like #point.rotate_y(PI * delta) for example.
$point.global_transform.origin = Vector3(1, 1, 1)
#point.rotate_y(PI * delta)
Thanks!