There is a component here
http://ltrees.codeplex.com/ that can handle trees.
From my initial poking around and questions on the discussion board, it looks like it is mainly designed for "walking aroung" scenarions, rather than flying. (due to the way the leaves are billboarded)
You could give it a try.
(it does funky animated trees as well).
J.
ps.. It can be frustrating, but you learn most when you have to get something going yourself, try starting off with a very simple objective, like
- I want to display a sample model at the origin.
Then look at the samples in the education section, and add code in to do the same thing in your project.
You will run into things that are tricky, or that don't work (like weird things to do with renderstate), and then you can either google or come here and ask.