Train travel planning can be difficult unless you can find good information. I usually go to http://mercurio.iet.unipi.it/misc/timetabl.html which is the Website for all the European National Railway. When I get there I use the Swiss timetable (SBB.ch) because it is the most user friendly. It will give you trial schedule for anywhere in Europe.

As far as when you will be traveling, it should not be to busy, but buy early is always the best way to go. If you know when you will be traveling you should be able to buy all your ticket upon arrival.

Have a good trip.

Greg