Hi!
I believe you would best be served by asking this question to the good folks in the Classic Trains section of this Forum. Its the first grouping (above Garden RRs) and the folks there are specialists on Lionel and AF and large scale trains.
ENJOY,
Mobilman44
ENJOY !
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
I've got one of the KW's. Tried to uncoil the cord after 30+ years in storage and wound up with two strands or bare wire with a plug on the end. I have yet to replace the cord but did disassemble the unit. You need to remove all of the levers on top. The two main levers can be removed after gently prying the center label off with a hobby knife. Once all of the levers are off, the screws can be removed and the entire bakelite housing will lift off. From there, you just de-solder the old cord and replace with a suitably sized new cord. reassemble and you're back in business. The green stuff sounds like corrosion. I guess cleaning it with a good contact cleaner may work. Just make sure it's good and dry before powering up.
Martin Myers