I just saw the movie on MGM-HD. Ok, so...he's next to the girl in the ready made coffin with his blood going through tubes while both are being sealed in a large box.
Did the "Darkness" part come about?
Did she turn into the girl he was trying to resurrected?
Odd, they just ended the movie with the police looking around the room thinking that he somehow vanished into thin air.
In the original, he was committing suicide. He's replacing his blood with embalming fluid, and expects to be with his wife for all eternity, both in death and in the afterlife. The 'Darkness' was hinted at when they shut off the lights at the end; they're both in everlasting darkness, sealed in their underground tomb.
In the sequel, he's putting himself into suspended animation. His wife's still dead, but he has a plan to ressurrect her and make them both immortal.