Adding stairs will greatly increase your time spent and also your cost. They also are more difficult to do properly. The wall will be 4.5' tall correct? This makes for a heck of a fall off the top. Will you be fencing it in? Perhaps you might want to build a double tier wall below the stairs and a single above. You can just lay a single elevation layer and it is generally faster and easier, but you will bury probably 2 pallets worth of block. Maybe just want to make a few steps of greater elevation.
All this said it generally is not recommended to build a wall of engineer required size your first time out. At least if you forked out a few hundred for the engineer you would know what certain dimensions to use. Sounds like you could pay for it out of the money you intend to use for overuse of geogrid and buried stone.