The one thing that may prove hard to overcome is that, as you remove the fridge-interior, usually moulded plastic sheets with a thick layer of expanded polystyrene as an insulator to hold the cold in, the cold will 'leak' out, placing more load on the cooling system.
You'll need to keep the amounts removed to a bare minimum, for it to work efficiently. Try taking a trip to a local plumber's/builders supplier and ask what sizes of 'piping grommets' they sell. That's the rubber-ring 'seals' that stop wires, pipes etc. from rubbing against sharp edges and seals the hole where things go through.
Keeping the DVD drive outside the case is a good idea, it will keep it at a constant temperature, preventing condensation as the tray opens/closes. I think the same applies to the PSU, too. They do get hot and, having mains-voltages around condensation is not recommended for continued happiness
.