I have bought nearly all my major video equipment (except editing systems) from B&H for a couple of decades. IMO, you can't go wrong by them. They keep their promises and treat their customers honestly and fairly.
I purchased my Phantom 2 and gimbal system for a GoPro from B&H. The gimbal had to be mounted and connected by me.
If you are at all mechanical, you should have no problem mounting the props on a Phantom 3 (just watch the RH/LH threads). Same for mounting and connecting the gimbal. Also, got prop guards. In total, it's about an hour's job, during which time you can charge batteries and get ready to fly.
I'm a 67 year old, so I come from a generation that believes in preparation. So, I'd suggest you also sleep on the thing overnight and read and understand the operation. For instance, understand the flashing lights and make sure you calibrate the compass before flying.
There are also excellent videos on YouTube that are better than if you were to stand behind a teacher to learn the basics. My favorite is <https://www.youtube.com/watch?v=UxtOMsIsezo>
Then of course there's the fact that even a caveman could operate this thing in Phantom/GPS mode (compared to the old days in the '60's when I had my last RC experiences). Just take baby steps and you'll be okay.
