This is the kind of view you see at various points around the forest. Definitely get a guide to go into the forest - not only do they know their way around the forest, but they can also tell you about the trees, animals and local culture. Usambara Eco Tours can provide a guide (they have a website). You will need to pay an entrance fee (the tour company can arrange for the payment to be made, as you don't actually go past a ticket office of any kind!)