3D Turret Rotation

I'm working on a game similar to Missile Command, where I have a 3D Turret that needs to rotate to the angle of the mouse (this will eventually be deployed to a tablet). Any good ways of doing this?

I also want to display the angle in text on the turret, so if there's a way I can use the angle found for rotation and store it in a variable, that'd be awesome.

Appreciate any help!!!!