I seem to have joined up during a change in the translation scheme, so I'm not sure if I'm missing anything or just riding a development wave out here. :)
I'm very early in the Spanish tree. Do I need to progress to a certain level before any buttons appear (on the tree or within a skill category) to go translate? Or are all translations now being done through the Immersion option on the main menu?
Yes, translations are in the process of being updated for all members. We are going to be always evolving the product, so it is something to keep in mind. We will also keep the community informed. You can see all the details in this update from the founder of Duolingo, Luis: http://duolingo.com/#/comment/180620 We've moved translations out of the lessons. You can find them in 'immersion' like you noticed :)
Will there be any way to get sentences or documents targeted to your skill level still?