If your comfortable tinkering a smoke unit is a doable thing. Get yourself some small magnetic #1 and #0 philips screwdrivers.
I do not own one of these atlantics but there has been numerous posts about "trimming the gasket" because it swells and rubs on the fan.
There have been numerous mentions of noisey or inoperable smoke unit fans. I had one on my legacy k4,got the three cab flashes indicating the fan was faulty,replaced the fan,diagnostic resets itself all is well.
I've been into nearly all of my smoke units at some point or another, at the very least if you regularly use smoke you'll need to replace the wicking at some point.So to some degree its a routine maintenance thing.
I'd start with the obvious, if you get the loco and the fan is quiet and stops after some operating time, check the gasket. If it works but is noisy, try a drop of oil on the motor shaft bushing, if it doesn't work at all replace it.
Lionel has plenty of parts available for these locos smoke unit or otherwise.
http://www.lionel.com/Customer...;q=11232&match=0