The track is not only clearly marked and easy to follow but graded and well cared for by DOC. As it is a Great Walk the track surface is well maintained for the 100's of thousands of walkers it sees each year.

The track map gives you information about drink stations, the route and the all important loo break. Click to enlarge.
To get some idea of how the race will challenge you, this profile map is a rough sample of the route from start to finish. Click to enlarge.
The Kepler Track is entirely within the Fiordland National park and is overseen by the Department of Conservation. For their description of this great walk and up-to-date information follow this link.
There are drink stations at all the major check-points which serve water, leppin, bananas and generally oranges, museli bars and jellybeans. All these are marked onthe race map along with loo points. Note that the Rainbow Reach toilet is across a short bridge off the main track - approx 100m return.

Put simply, the full Kepler goes up sharply, down steeply then tailing off to a long slow incline. The steepest and potentially most treacherous part are the long stairs down from the Hanging Valley shelter. These are in 6 sections and around 200 steps in total.