I'm going to Munich on July 13th to see live the Katzenjammer @ Tollwood Festival. I'm departing from Vicenza - Italy, but I can't find how to get to Munich from there by train. I want to buy the train ticket before travelling to Europe.
This will certainly give your schedule options - http://www.bahn.de/i/view/GBR/en/index.shtml but not the ability to purchase.
Whether Trenitalia's website will permit purchase for international travel on their website or you purchase from RailEurope or at the station, and whether there is discounting for advance purchasing, I could not say, as I am not familiar with the two countries.
If you still have a problem Tripadvisor has a Train Forum.
Travelling from Vicenza to Munich by train will roughly take 6,3 hours. You first have to take a train to Verona and then you can take a direct train from Verona to Munich.
You can buy the tickets from the german Railway website (www.bahn.de). They also have an English version of the site. The sooner you order your tickets, the cheaper it usually is.