We did not particularly dived into the history of the city, since it is quite large and it is impossible to see everything in 2-3 hours. Just walked along the streets. There are quite a lot of tourists, so even if you want to do deep investigation, it's not easy.
If you are fun of such places, then come definitely for the whole day or even for a few days. Take audioguide on site or download one on the Internet.
http://pompeiisites.org/en/visiting-info/map-and-guide-to-the-excavations/ - updated maps of the complex.
http://pompeiisites.org/en/visiting-info/timetables-and-tickets/ - opening hours and ticket price.
Getting there: paid parking in front of the entrance N 40 44.815 E 14 28.996. Pompeii is located on the Naples - Sorrento railway line. There are fast and slow trains, you can get in 30-40 minutes from either side, get off at the Pompei Scavi (Villa dei Misteri) stop. There is a luggage storage office at the station. Read here details on how to get to Pompeii from Naples.