rico,
Yes, it sounds like the orfice tube is clogged, but simply replacing it is not the solution. When an orfice tube cloggs up it means something else has failed and the debris has gotten stuck in the orfice tube.
It could be something as simple as ait getting into the system and forming ice which blocks the orfice tube, or it could be that the compressor is failing. Many parts in modern AC systems are teflon coated and when they fail the teflon flakes off and migrates troughtout the system. The system will likely need to be dismantled, and checked for debris and where the debris came from (compressor is the most common problem) The system needs to be cleaned and flushed out, the orfice tube, and Accumulator/dryer replaced along with the failed part, and the system evacuated and recharged with refrigerant, and compressor oil.
Depending upon what part actually failed, you are probably looking at about $500-$700
minimum for repairs.
Often times, the compressor failure will clogg up the evaporator and or condensor cores so bad that they cannot be cleaned out and need to be replaced. The compressor, condensor and evaporator are the main components of the AC system and replacing all of them could easily run $2000 or more.
...Rich