There's a very knowledgeable guy that frequents this board with the handle of "CountryGent55". He sent me more info on adding remotes to my 1965 JD1010RU than I even understand.
As for the drain plug it should be on the back of the rockshaft housing. The filler cap should be under the front of the seat.
For what its worth, I was told by the local JohnDeere dealer that adding remotes or front loaders is only recommended on a dual cylinder system like the RU models have.
Is this an absolute fact, I have no idea.