When you stay "stairs" does this mean a series of individual steps that are not connected to each other?
What are the existing ones made of? Do you want the new ones to be made of the same material?
I think you're saying you want to replace a bunch of individual steps without messing up the ground and slope of the area. My only suggestion is to do one at a time rather than tear it all out before replacing any.

The stairs are the hill. The set up is every two feet there is another stair, the step up consists of two boards placed in the side of the hill. In between each step is dirt until the next set of boards for the next step up. The stairs are nothing more than hill itself and that is why the they have become so unlevel and eroded. I am not sure that there is an actual way of keeping that natural look and keeping the gradual rise but I sure like to try. I was thinking of putting boards on side or even brick as a trimmer or outline of the steps and placing mulch between each step up, but the question is will this keep after a few years of weathering? I dont want to be in the same place i am in now two years down the road. Thanks for your reply.

i am terracing my backyard and need ideas on building stairs aprox. 10 feet high and going back 15 feet