Immigration and customs in FRA T2 tend to be fairly quick, with some early morning exceptions if you arrive at the same time as Ukraine International or Aeroflot, which can delay immigration.
There is no train station in T2. You would take a inter-terminal train over to T1 where you can take a train from the main train station (Fernbahnhof) or the regional train station (Regionalbahnhof). The regional trains connect you to Frankfurt's main train station (Hauptbahnhof), from where you'll likely have more and better connections to Munich. Alternatively you can take a taxi from T2 to Hauptbahnhof (ca 15 mins and €25-30).
Another alternative would be to take a Lufthansa flight from T1 to Munich.