I had outside fans but when the cooling unit failed the Service Tech who helped to replace it (it really is a two person job and she'd done it before) showed me where "Crud" (Fiberous stuff) was building up on the lower side of the heat exchanger (outside).. NOTE that it was no where near critical and now that I know how to clean it easy to blow it out but.... another 10 years it might have been a problem.
Inside fans (link follows) do a fantastic job and lessen the need for defrosting.. The set I have is 3 fans (My Fridge really needs one more and it will get it. possibly soon as I have the fan) the circulating air keeps the frost down.. Instructions say to run the power lead out the drain hose but ... I hooked to as someone up-thread suggested the HOT side of the interior light Work great
not the fan I have but close