I agree, you have plenty of time to prep. Don't worry about placement, etc. It won't do much good to worry about a problem that may never materialize. For now, focus mostly on your studies, and begin to explore different schools that you may want to apply to. Depending on your summer plans, you can focus on preparing for the GRE over the summer, and then take the GRE at the end of the summer. You'll want to study vocab and also get very familiar with the structure of the test. Princeton Review is very good for test strategy, so when it comes time to prepare, try Cracking the GRE. Excellent, excellent guide to the GRE.
For now, though, just don't worry!