I started building a rollercoaster and I started the track, after the station, going left and it built throughout at least 3 hours of building. When i was finished I tested the coaster, only to see that the cars were facing the wrong way and it started going the opposite way I wanted it to... Is there anyway to change the way the cars go?

Are you sure the coaster is not running in reverse-incline shuttle mode? If you're running one of the continuous circuit modes, it would mean you would have had to have built the entire coaster in reverse, meaning every direction of every track piece would have been noticeably reversed (i.e. to make the track go upwards, you would have had to click the downwards button, etc).

What does the coaster look like?

Take a screenshot using F10 and post a picture.

Open the coaster menu and tell us some of the track specs.