writing an article on general relativity has been one of my mid to long term goals, but there's not much foundation in Citizendium in differential geometry yet.
Why not just start by broadly explaining the equation (like, f.i. saying something to the effect that "The left side of the equation basically tells point particles what a [[straight line]] is in the hilly landscape of [[spacetime]], or actually how they should move around, while the right side - known as the '[[stress energy tensor]]' basically describes how matter is distributed and moving around ... So what the theory basically says is that how particles move due to gravity is decided by how local matter/energy is distributed and how it moves... ").
Then you can just write sections into the dif geo article as needs arise and as you take your time elaborating the article, perhaps adding separate articles on the stress energy tensor and the einstein tensor.
Just a suggestion ...
Btw, GR can AFAIK be formulated without using the dif geo framework, think I heard somewhere that Steven Weinberg has done just that.
Greetings, ragnar.