how can i fix my moffat refrigerator?

My refrigerator suddenly stopped producing cold air. The freezer doesn't freeze anymore and the refrigerator is warm. It is an old make, a Moffat MRF1739W-5, Ser FE136247, volts 115, amps 5.2/6.4, Hz 60. It's CANCO inc., and made in Canada. I noticed that the engine in the back off the fridge is extremely hot and the bottom of the fridge is very rusty. The refrigerator still produces air and the light still turns on. How do i figure out what's wrong with my refrigerator and fix it. Thank you.