If you are a guest at MRL then this cache should be an easy find for you. If you are in the park but staying elsewhere you will need to contact the manager of MRL to gain special access to the lodge before you can look for the cache. I spoke with the managers (Astrid & Chris Haas) during my visit and they are happy to maintain this cache for me.
When you finally arrive at GZ, you will find the geocache behind a tree behind the seat. There is no need to go near the edge. Make sure you relax for a while and take in the beautiful views while you are here.