HORRIBLE NOISE

I have a GE Gss22jf we had a repair guy come over to look at it because it is really noisy, he said it needs an Evaporator Motor, an ADC Controller and a defrost element at approx $800 this sounds expensive, can I buy the parts online and fix it myself? the only parts I found that sound like these are an evaporator fan motor, a defrost heater element, and the ADC Controller, how will I know if I am buying the right parts? any suggested sites for purchasing these?