keeping things cold just barely cool

Mr. Mayer, I have a Frigidaire 3.1-cu ft Freestanding Mini Fridge Freezer Compartment as found at Lowes. I bought it used but don't think its that old. Date Code is 16W10 if that helps. I have it at work and it has just stopped working right. At first we heard a fan type noise that didn't sound right and sounded like it was coming from the freezer area. Then it just was not keeping things cold just barely cool. I turned it off last thursday and have not turned it back on yet. The drip pan, that wont come out, has a lot of smelly water in it. Smells like someone crapped their pants which is what I thought at first LOL. How do I trouble shoot the cooling issue and what do you suggest to do about the standing water that smells?