1) You can get your tickets at the station. Looking online at a specific time? Fuck those. They are more like guidelines. Your ticket is good for the entire day, from the starting point to the destination that you bought if for.
2) Transfer: Get a map and a timetable. The transfer points are listed on your tickets. Or, read the timetable – or electronic sign of upcoming trains when you get off the train at your transfer point to see the platform and time of your next train. 1st class or 2nd class. If you want seats that are slightly less comfortable, for a lot less, look for the obvious “2” that is on the trains themselves.
3) A conductor will come around and punch your ticket. You don’t need to be searching around for a machine to scan it through and wondering if you accidentally made it onto the train without paying and are going to be booted off. And yes, you can eat and drink on the train. So open up a snack, lean back, (metaphorically – the seats don’t actually lean back) and enjoy the ride. Or you can stand there with your backpack on for an hour by the door like an ass, thinking the ride would only take 5 minutes, and then be too stubborn to go find a seat after the realization that it was going to take much longer.
Having never ridden Euro Rail, I had the misconception that you bought a seat, at a specific time. It reminds me more like the US subway or metro system, which made it easier for me once I figured that out.