I want to create astronaute expeirence for VR. How should I tackle it?

Hello guys!

I'm relativley new to Unity, but i'm quite expeirenced developer with strong understanding of coding. So, i've fiddled around with Unity for while and managed to create some little games. However, I do have a dream which I make Astronaute experiance. The general idea is to play him on space, starting from space walk, entering to space station and manage to espace it while it blowing up, and flying the probe back to earth.

So there are the major roadblocks infront of me, and i'd really happy if you could give me some directions how to tackle it:

1. Earth & Moon - I want earth be visible ALL the time in background, with active weather and day/night cycle, and continents in high resolution. Moon should be visible but player won't go by it, so it could be low res model with no special additions, expect the fact it could be influenced by earth and sun. (shadows) How is possible to create huge objects, or at least make them feel really really big? I envision the player floating over earth while it covering almost all 180% degrees of view.

2. VR project - At first i'll target it for SAMSUNG Gear VR (since I don't own Rift, for now). so I gotta to manage the game under reasonable resources for smooth VR experience.

3. Landing on earth - I've seen and read some tutorials around procedural planets and full size planets landscapes. Its not the case here - I want drive the player via very specific route back to earth, on certain time and area. So I won't need to give high details to 90% of earth as player getting close. Also, I want to emulate atmosphere entrance, with heat damage and altitude, all of those planetary landing factors.

Also, i'd like you know i'm not really strong yet on Unity terms, so I'd be really happy if you can explain me shortcuts and terms while explaining me :)

Anyway, I've been thinking on solution but I'm not sure if I any close to good - Splitting the game into levels and loading them at different parts - for example, space walk sequence will feature high-level details spaceship, with interior features, while earth is just huge sphere with high details textures, and few clouds floating above, the descending sequence will feature small part of earth with high resolution terrain and textures (the descending route), and finally the actual landing will feature "regular" level settings where player just dropping with parachute into the sea.

Your turn guys. Let me know how should I tackle such a project!