Help, new 2001 4runner owner

We just purchased a 2001 4Runner SR5. I love this thing! Best I have ever driven and most fun. I have questions. I want MORE fun. It had 12K mi on it when we bought it last week. Its perfect. I have questions--please don't laugh at my ignorance:

1--how to get it from H to L4? Shifter will NOT budge.
2--Book says to drive in 4wd at least 10mi/mo...can I drive in 4wd more often without damage? The power of 4wd is awesome.
3--How to tell if the deferential is locked?
4--Any advice or recommendations?
5--How do you drive? H unlocked? H locked? L4.....