Well, there is plenty of info if you do a search - maybe too much to wade through.
1. Amsoil is one of the best, some would say THE best. I use Mobil 1 just because it is a little cheaper and a LOT easier to obtain. Other great brands are Redline, Silkolene and Bel Ray. Castrol Syntec is pretty good as well and again cheap and easy to find.
2. Controversy - do a search. I use 5w-30 but am thinking of switching to 0w-40. The owner's manual is totally ambiguous.
3. Purolator. Avoid Fram.
4. Yes, it is recommended (by me anyway!!) to switch to synthetic. Again, a search will reveal reams of discussion.
5. Controversy again. Some say 7000, some 10k. I change mine every 2k - 3k but I'm anal about engine lubrication (and have motors with 200k on them that look new inside!).