i think that you might want to look in to a crf 250 or 450 if you are going to be riding the dunes as well. because a 230 is good for the trails but that is about it.
utilities can be fun but a 250 is not much for a utility but it would have 4 wheel drive. a 2X4 is fun and can go in some mud but not much, they can go fast and are a ton of fun. see if you could get a 450 instead though. pick the one that you want we can not help you pick what you like we can...
to shift gears you let off the gas a little pull in the clutch pull up on the shifter then let out on the clutch and give it the gas. you should be all set. and yes you need to do this for all five gears.