Two weeks ago my fridge began making noises and whining. It sounded like there was a puppy in the fridge. Then, at the end of last week the fridge just wasn't cold enough. It is cool, but it is turned all the way up and just not cold. Any ideas on what needs to be replaced? Compressor? Thermostat? Both? Is this a hard installation? Are special tools needed? How long will it take? Once I replace the broken parts will everything be ok, or will I need to charge it with Free-on or some other coolant?