1. Yes; BMW says our plugs can go for 160,000 kms (72K kms for 135's) but most knowledgeable people say about 100K kms is better.
2. No
3. Believe not with our N52 engine
4. Yes
5. 1/8th turn then torque to spec in Bentley manual
As far as videos, both Bavarian Autosport and Pelican Parts put out real good DIY's.
https://www.bavauto.com/diy_videos