You can reach Oberammergau by train from Munich central station (München Hauptbahnhof), you have to take the train headed to Innsbruck (a regional train that departs on daily basis) and switch trains in the Murnau train station (the train to Oberammergau is the only other train in the station), the trip from Murnau to Oberammergau shouldn't be a problem, since Oberammergau is the last station to be reached.
You may also reach Oberammergau by car, you would have to go to south Munich in order to the take the Autobahn A-95 south to the Ettal exit. From there on the B-23 to Oberammergau.
Getting around Oberammergau shouldn't be a problem since it's a relativly small town. You can get around (as most locals do) walking, but you can also take the bus (there are a couple of bus stops in town), you could also get around by car, and like most of youth by bicycle.
For a small town Oberammergau offers a great variaty of places to eat. If you don't wish to spent too much money in food you can try eating at one of the imbiss (bars in which food is also served). You can also eat at one of the many hotel and guest houses (where among international food, local food is also served). There are also classical choices of food, for instances you can eat some of the best burguers in Charlys Imbiss or if you're in the mood you should try el Puente (a mexican restaurant). Desserts are to be found not only in the restaurants but also in some cafés.
Hot beverages are served in the small cafés in town. There are also Café/Ice shops in which coffee and ice creams are sold all year round. But if you'd like to have a nightcap then you probably would want to go to some of the town's bars, if you're young and just want to relax among young people you should go to the Kino Cafe (a movie theater with a café), in here you're most likely to find any kind of cocktail you want and also some good food. But if you want to expirience some of the local folklore then Zum Tonis is the right place for you, a typical Bavarian bar, with a friendly staff and a large variaty of local and international schnapps.