Assuming that you have cold/cool food and your old unit is DOA there
are several things that you can do:
1. Using a clean container (or one lined with clean plastic) ice down
your food to keep it as cool as possible. Try to keep it all in one
mass. Plan to consume refrigerated items soon.
2. Assuming that you kept the unit upright in transit, plug it in and
set it a bit colder than normal. Make sure that air can circulate well
around the cooling coils. Leave the icemaker turned off for now. Point
a fan to blow air over the coils to increase heat rejection.
3. Once the new unit has cooled a bit, start moving the frozen foods to
the freezer compartment. Hopefully they are still frozen and a
refrigerator cools "something" better than it does just cooling the air
4. After the refrigerator side has cooled a bit more, begin placing
refrigerator goods in place. Increase the thermal mass this way.
5. Once the unit is fully loaded and is not running continuously,
connect and start the icemaker.