If I were you, I'd pay a competant RV service guy to properly diagnose and fix what's wrong, it might be a small cost fix as described above. Yellow green stains and ammonia smell means dead cooling unit. If the cooling unit is shot, it can cost around $800 and you may be successful in installing it yourself, not "a piece of cake". We had a new Norcold fridge installed for $1400. The mobile service guy had problems. The new fridge didn't cool, he installed another one, it didn't work either. He had to take fridge out, turn it upside down to get coolant into the right place and then it worked. Sometimes this turning upside down treatment will get an old cooling unit working.
