Frank's link is our catalog of "good info on the MR" here.

Answering the questions:
1. Probably not, but watch trip reports closer to your hike.
2. The links in the link above.
3. Guides all do. Few private groups do, unless more experienced people are leading new hikers.
4. Upper Boy Scout has nice spots, so does Iceberg. UBS is easier because you don't need to haul your gear so high. It still puts the summit well within day hike range. Many will summit, return to UBSL and break camp and hike out. At Iceberg, you are higher -- high enough that if you aren't acclimated, you can wake up feeling pretty foul.
5. If you're camping overnight, you need to return the same way so you can haul out your gear. People who day hike the MR will often return via the main trail.
6. The Final 400 sounds like your fun "cup of tea".