If you have taken an item from your refrigerator and it appeared warmer than it should be, and on subsequent days items and the internal temperature of the refrigerator appeared to be getting warmer, its likely NOT time to replace your refrigerator. The following steps will help you decide what to do:

1. Check to see if the freezer portion of the refrigerator is cold and everything is still frozen. If it is also warm, it's likely time to replace the refrigerator. If all is well and everything is still frozen, transfer the food to another refrigerator or an ice chest (with ice) and unplug the malfunctioning refrigerator. Leave the doors of the unit open.
2. After half a day, remove the cover at the bottom of the front of the refrigerator (under the door) and with a flashlight, check how much water has accumulated in the pan in the bottom of the refrigerator where water from the defrost cycle drains. If there is a considerable amount of water, the problem is likely a malfunctioning defrost cycle timer. When this timer malfunctions, the refrigerator doesn't defrost and ice builds up on the evaporator (usually located behind the wall of the freezer - this is what causes the cooling) and this ice buildup starts restricting air flow down to the lower refrigerator causing the temperature to rise - the freezer remains cold. When you unplug the refrigerator, it causes this ice buildup to melt and air can again flow to the lower refrigerator.
3. Leave the refrigerator unplugged to let the ice block melt. When it appears to be melted (no more water run-off into the defrost pan), turn the refrigerator control dial to "off" and plug the refrigerator back in. Turn the dial to "on" and close the doors.
4. After two hours, check the temperature of the lower portion of the refrigerator. If it is cold, the problem is the defrost timer and you need to get it replaced or the ice will build back up again any you'll have the same problem.
5. If you are not mechanically inclined, call an appliance repair shop and tell them you need your defrost cycle timer replaced - give them the make and model of your refrigerator so they can bring the correct replacement timer. If you are handy with tools, find an appliance parts store in the yellow pages and call them to ask if they have a replacement defrost timer for the make and model of your refrigerator.
6. The defrost timer will usually be accessible through the front of the opening under the refrigerator door (you removed the cover earlier). The timer is a small unit with a number of electrical wires going into it. Unplug the refrigerator and remove the wires from the timer and then remove the timer. Take it with you to the appliance parts store to be sure you get a replacement part that will work - it doesn't need to look identical to the malfunctioning part.
7. Reinstall the timer and reconnect the wires.
8. Turn the refrigerator control dial to "off" and plug in the refrigerator.
9. Turn the control to "on", close the doors, and let the unit run .
10. After two hours check the temperatures. Both compartments should be cold.
11. Replace the cover on the front of the unit.
12. Check the temperature of the refrigerator a couple of times a day for the next couple of days to be certain this indeed fixed the problem.