I had bought a replacement chassis a few years back from Bachmann for The Big Hauler, with the intentions of changing out a very old one on my sons original unit. Well life got in the way, but when ordering some other parts, I saw this: Loco Shell - Denver&Rio Grande Western (G 4-6-0 Anniversary) [810XX-81088] - $39.95 : Bachmann Trains Online Store! So for $40 I’m just gonna put it one that new chassis which has the metal rods I had and just like a new engine. And a color to match some cars I have.
Go for it, I’m a modeler and rebuild/refresh all my locos and rolling stock. Who knows, you just might become a modeler and have great looking and running railroad models. For me the best part of the hobby.