freezer is working, coils are defrosting properly but refg. is not cooling very well.
Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=mzd2766ge
Check the freezer temperature, should be around 0 degrees F.
Check the fresh food section, should be about 40 degrees F
If freezer temp is OK check that the damper door is open and there is nothing obstructing the air flow.
Check that nothing is blocking the air return vent between the freezer and the fresh food sections.
Check that the evaporator fan in the freezer is running OK.
Check that the condenser/compressor fan is OK and that the coils are clean.
Is the compressor cycling as it should?
The above of course assumes that there is not a defrost problem.
Here are couple good sites with basic fridge repair info.
http://www.applianceaid.com/frig.html
http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php