You'll be exclusively using T2 then. IMO, it is the nicer of the two terminals. You will need to clear immigration and I'm assuming that any bags you checked will continue straight through to Paris.

Immigration in MUC has for me been very easy. There has been a line, but it usually moves very smoothly and I doubt you would spend more than ten minutes or so in line. Once you get out into the arrivals hall, look for the signs for the train station. It is located in between the two terminals and is very easy to find.

The train ride itself will take around 40 minutes to get to central Munich (Marienplatz or Karlsplatz/Stachus). You will want the S8. The S1 also goes into central Munich but the route is a little longer.

In theory, you could spend all of that time at the airport. But, I would want to get out and see a little bit of Munich, too. You can buy a day ticket for the S-bahn that will cost you in the neighborhood of 8 euro apiece. Make sure you stamp the ticket at one of the 'stamping' machines on the platform.