A few things:
1. Car is M54B25.
2. Manifold is M54B30. You need an M54B30 Manifold, B30 DISA and B30 Throttle body, probably need the boots and the MAF from the B30 as well as an airbox to fit the new 3.5" intake tract.
3. The M54 is Drive-By-Wire.
4. Yes. Research.
Truth be told, you won't really gain all that much. Something around 6 whp. Wouldn't waste my time getting dirty unless you seriously know what you're doing or what the end goal for the car is. A non-M will never be fast. I would focus on Suspension upgrades and cosmetic enhancements.