I give myself the Rebif shots and they are not a big deal. I used to do Avonex and that was a lot harder, I needed someone to do them for me. With the Rebif I have the auto injector which is awesome! You don't see the needle go in and all you have to do is push a button and it does it itself.
As for giving it at night, that is because of the side effects from the shot. If you give it at night then most likely you will sleep through most of them. I give myself the shot around dinner time, I take Tylenol 1/2 hour before the shot and then again 4 hours later to lessen the side effects.
I know the diagnosis is scary enough for you, never mind giving yourself a shot. We are all here for you if you have any questions or need to vent!