I'm sorry you are having this problem with your refrigerator. You have received some good general information from James. This type of problem will normally be due to poor air flow. First check for a heavy frost build up on the back wall in the freezer. If you notice a thick frost accumulation, this will be a defrost related problem. This can be caused from the defrost control board, the element or the bi-metal. In this case, you can open the door and turn the unit off for several hours to allow it time to defrost. When all the frost is gone from the front and behind the panel, it will cool ok again until the frost builds back up. This will take a few days and allow time to get it checked.
If there is no frost accumulation, then this will probably be a problem with the damper in the air diffuser not opening. In this case, there is a complete control panel assembly # 5303918283 that would correct this problem. A technician will be needed to install this kit. I'm listing a site you can access, to have a tech come out. Here is a link for the website:
Sears Home Services
. Now, if you can gain access to the air diffuser (# 115 in picture) and if the damper inside is closed, you can wedge it open temporarily so the fridge section will cool. If you would like more assistance, any additional details will be helpful and I will be glad to assist you further.