Will I like this game? And a few questions.

I got this game yesterday, played for like 40 minutes saying "holy sh!t I have never seen words like this before" I do enjoy physics and games that are challenging and make you think / be creative. But god damn I have never been so confused. Anyways some questions.

1: I see some people with around 1000 hours playtime, what makes up the majority of this time, (building spaceplanes, modding)

2: How long did it take you to get a basic understanding of the game and how long to learn all the advanced stuff?

3: Whats the best way to learn the game? I am trying the tutorial but getting stuck on basic things like stopping my space plane from spinning after that bastard von kerman guy nudges it, and making my orbit thing go to the... Mun orbit or something.

4: are there mods for the game you can stuff around with after finishing the story mode or something?

5: also, are there any DLCs for the game, im looking around and seeing submarines and cool stuff.

Thanks This looks like the right place to ask stuff, if anyone gets pissed off i can take this down.