Swapping to an electronic control is easy.

Now if you are finding the top speed too fast using the stock gearbox, just swap out the stock 500 Mabuchi for an Integy 45t, 55t or 65t motor. They originally made the 55t for their comm lathe, but crawlers loved the torque, so they went ahead and added two others. All have FULL bearings and are rebuildable (replacable brushes and openable to repair)

Any simple reversable R/C car ESC will do, but I'd suggest one that has a delay between forward and reverse. Saves breaking tracks, though plastic tracks are fairly cheap these days.

Check in the turret, you may have a flash unit that often came with the King Tiger, and its just not hooked up. I can show ya what it shoukld look like, got a trio of 'em for my special projects.

Its fully usable, just not capable of battling, and not worth upgrading for battle unless you're handy hobby-wise.

If you trade it away, make sure you get a Full Function (Smoke and sound) HL out of it... fully operable with metal gearboxes and tracks, if possible. Its worth at least that.