Congratulations. It's a great bike.

I always rode alone. Had too or I didn't ride often enough. You can carry a cell phone or tell some one where you'll be and what time you'll contact them when you return. It's of course better to have some one with you if you can.

IMO the best thing you can do is get Ned Overend's book Mountain Bike Like a Champion and the second, get Brian Lopes book Mastering Mountain Bike Skills.

I put Overends book first as it emphasizes those things that will keep you safe up front. Most serious injuries apparently occur at low speed and he deals with that. Lopes book is full of excellent photos demonstrating the stuff in both books. Overend's book can probably be bought used form Amazon for a few bucks as it's been out a long time.

The reason for the books is to accelerate the learning process. You can start off right away using good technique and don't have to unlearn bad habits later. Another reason is you'll get faster quicker and speed makes riding much more fun. That really helps the motivation to ride and to continue improving.

Al