First time on a train.."not getting any help in the right section)..help me please?

I live in Montclair and need to get to Sun Valley. According to the Metrolink website I will have to depart from Pomona union station, get off at Los Angeles Union station and depart once again from there to Lancaster union station. The trip is estimated to be a little over 2.5 hours. Anyway I have no problem with figuring out how to find my way and make sure I take the right train (I'm sure their employees/condutor will be glad to help)..my main question is will I need to pay for each train? My friend said it's 18$ to go to Los Angeles AND back. Will I need to pay another 18$ or more to take the second train to Lancaster? Or is there maybe an "all-day" pass I could purchase like they do on buses? Any feedback would be great. Please and Thank you.