Already been there. He doesn't really explain the methodology. My case involved 2 adjacent edges, not opposite ones, and there's also no explaination of exactly HOW to flip a single edge.
To swap two adjacent edges, simply do the swap described on my page. This leaves you with a position where three edges are wrong. This can be solved the same as on a normal cube.
To apparently flip a single edge, you must also flip one (or three) of the edges in the middle layer (assuming those are the flat edge pieces with one colour).
One way to do this is (ER)4, where E is an eastwards turn of the middle layer.