Yes, you need to take the PSAT (in 11th grade) for NMSF. Since the College Board keeps all SAT sittings that you take from 9th grade on, and since some colleges require that you send all test scores, it is better to take the PSAT as a 9th grader. The PSAT is not sent to colleges. If you top out the PSAT, then you know you're probably good for NMSF and will do well on the SAT.
If you want to take the SAT, there are usually organizations and test prep companies that will offer a practice SAT in real test-like setting. Just make sure the test company didn't make up the questions - make sure it is an official practice SAT or a past released test.
