Glen Ellen has a lot of history. Glen Ellen began as a 1,000 acre parcel of land that was purchased and named "Glen Ellen" after the wine maker's wife. As the town grew it became known as Glen Ellen. This is also the home of one of the "Hidden Gems" of Sonoma County. Yes...I am talking about Jack London State Historic Park. This has been one of my favorite places to visit and to hike. I know most people think of it as the location that Jack London had his ranch and where he wrote his books. It is so much more than that. There are over 1400 acres of trails that go to the top of Sonoma Mountain where you will find some of the best views available.
Now about the multi...
Stage one is a benchmark. Take a picture of the benchmark and log it on geocaching.com. Using the information located on the benchmark solve for the final location. The final location is close enough to the benchmark that you don't have to cheat and look at the pictures of the benchmark that people have uploaded. Besides, if you stand on top of the benchmark and take a good look around it may help you with the puzzle. You can log the benchmark at http://www.geocaching.com/mark/details.aspx?PID=JT0860
Now that you have found the final location you will need to simply find a way to get the cache in your hand. If worst comes to worst...at least you will get to log a benchmark! 
You will need a flashlight and a skateboard or knee pads...although the skateboard is a much more rewarding experience, and quite a bit easier.
The difficulty rating is based on the need for special equipment and for the field puzzle which you will understand when you are at GZ. You may experience muggle issues when trying to do your subterranean exploration. I have been there three times and had issues twice. The second time I just ignored them and went in anyway. It may look strange...but they certainly are not going to go in and explore themselves.