Before you spend money trying to repair the appliance, give Samsung a call and tell them about the cooling problem and the noise from the fan.
They should come and repair the appliance free of charge.
The warranty for cooling faults in the fridge on the RS21 model was extended to 5 years. (I have heard of appliances 7 years old still being repaired for free). I believe your model may be included too.
The problem is normally a fault with the defrost system.
Samsung will replace the cover, fan, thermal fuse and defrost sensor.
While you are on the phone to Samsung, ask them if your machine is one of the machines on the recall list.
If it is, they will do a modification to your appliance free of charge.
If you have problems with them, let me know and I'll advise on what parts you need to try and cure the problem.
Hope this helps
Let me know how it goes or if you need more help