@PilotRockey Here is the what I can tell you from my time spent on the 717 flight deck with Citrus.
1: The biggest thing is that engine bleeds are dynamic based on N1. As the engine spools up, the packs get louder. Vice versa when they are idled down.
2: Engine sound is barely noticeable from the flight deck as the engines are so far back. You can hear them, but they are quiet compared to the avionics cooling fans and a/c. And as airspeed increases, you can no longer hear the engines. As a matter of fact, the only thing you can really hear at cruise is the wind stream and a/c.
3: You are correct about the ground roll from the main gear. Nose gear rumble is quite present though since you're basically sitting right on top of the nose gear strut/bay. When the gear is raised, the only real noise is the "thunk" of the doors closing. When you lower the gear, it's kind of a thunk-woosh-rumble sound...lol.
Let me know if I can help you any. It's been quite awhile, but I still remember her for the most part.