I think my alternator has failed and I'm wondering how much of a hassle it's going to be to replace?

The motor is a 3.6 with stock injection. Can the alt be swapped with the engine in the car?

I'm assuming it's my alt, I have 12v while the engine is off and the voltage drops to 11.45v while running at idle and drops slightly from there as rpms increase. I can't imagine what else it could be. (Ok,,,it could be regulator but that's in the alt anyway) Seems odd it would just go, but I guess that's how they go

Any advice welcome.......Thanks!