If you start playing the sicilian, I wouldn't recommend to become familiar with Najdorf and Sveshnikov. Both are very complex openings and it takes a huge amount of time to get familiar even with the main lines in both of them.
Apart, I can recommend several things:
1.) To get familiar with plans more then variations, the best thing is to analyse games from strong players who plays Najdorf/Sveshnikov. For Najdorf I can recommend to take a look at a number of Vachier-Lagraves games.
2.) A good book for 1800-1900 is usually the Starting Out Najdorf book from Richard Palliser. It's not really up to date, but I think below 2200 that doesn't really matter and gaining an understanding of the structures and the positions is much more important.
3.) Another good ressource for the Najdorf is the PowerPlay DVD from Daniel King.
He also has a quite good DVD for anti sicilians.
4.) One of the best Sveshnikov books is the quite old "Sveshnikov Reloaded" from Dorian Rogozenko.
That are more or less the ressources I can recommend based on the given informations.
Be aware, that Bb5+ variation after d6 doesn't help you much if you want to play the Sveshnikov.