Wow, surprised you got a brand new one with 4.3.1 on it! Short answer is no you can't upgrade to 4.3.3. Since you just got your device you won't have saved blobs for 4.3.3, which you need and are specific to each individual device so you can’t use someone else’s. You will have to wait for a jailbreak for 5.0 to come out. They are working on it but there is no ETA and whatever you do, don't start a thread asking when it will be out When it's released it will be in the thread SweetPoison linked to and I'm sure there will be an announcement on the homepage of this website.