My 6yrs old upright frostfree freezer doesn't blow cold air anymore?

My 6yrs old upright frostfree freezer doesn't blow cold air?
Hello`,I have a 200 litre Westinghouse freezer frostfree model FJ20BS that I bought 6 years ago and all the sudden it stopped cooling.I went to get something out and everything was defrosted.I thought that maybe I left the door open by mistake, but wasn't that.Everything seems to work but the air blown by the fan is not cold.I check the temperature settings and changed to HIGH,but nothing changed.The technician reckons that the compressor has a lead valve broken and that I have to replace it all (and charged me 90$ just to tell me that!!!).But it seems strange to me,as it's not that old and how could it break like that? I'd like to get a second opinion and see to check if it could be something else instead or if it could be fixed withoth having to replace the all compressor.Do you have any suggestion?