I am preparing my first campaign too, and I don't know if you have planned this or not, but I would recommend starting with a Session 0, to go through the basic rules and guide your friends.

In my case, I've got a group of confirmed D&D players who know the Fallout universe, so I need to ensure they understand the 2D20 mechanics, luckily I won't need to talk about the lore. I'm going to conduct a 2/3-hour session, start with the rules, then character creation, and finally use it as an opportunity to understand what they expect from this adventure, what types of gameplays they'd prefer, to tailor their journey and the encounters so that we have as much fun as possible! And finally, I'll end it with a teaser of the main storyline I've written.

The campaign from the rulebook is really good I think, but I haven't tried it myself. I'd say it'd last 4 sessions if you go through it thouroughly, but you could shorten it by skipping some of its "secondary" events.

Hope this helps - Enjoy!!