One of my favorite trains made by Lionel in the MPC/Fundimensions era was the Chicago & Alton Red Train from 1981. I loved the attractive cherry red and maroon paint scheme on the locomotive and the matching 9500 passenger cars. I purchased a set from Christopher2035 here on the forum for a pretty good price not very long ago, minus the scarce dining car.
However, since my passion was more towards scale and command control, I considered selling it in favor of a Lionel Legacy Alton Pacific. But then I figured it would be far less expensive to upgrade the set I had to TMCC, and get a handsome train that I could run with the Legacy and still negotiate O-31 curves.
Starting with the locomotive, the first thing to go was the mechanical E-unit (no more obtrusive lever through the top of the boiler). Over the years, the wiring to the pick up rollers became cracked and dry, so I replaced those wires. I soldered a 4 pin connector to the field winding and the brushes, along with the capacitor lugs. I covered them with electrical tape just to make sure they'd stay secure. I kept the original smoke unit, since it still worked well, and I didn't need synchronized fan smoke in an engine like this.
Next, the tender, where most of the work went on. I was really happy to get rid of the Mighty Sound of Steam, and used Goo-Gone to remove the very annoying foam that had a tendency to disintegrate. The tender was actually quite small, so fitting all the electronics was more of a math problem. Since Lionel offered the American Flyer Alton RailSounds chip on their parts inventory site, I chose that for the sound system - thankfully, in this case, it matched the engine's road number, too! The rest was pretty standard, and pretty much the same as how I upgraded my Lionel Southern Mikado.
Now I have an engine that runs great, sounds much better, and can run alongside my scale equipment and not feel too out of place. 
