You can start with 1 or 2, but know that 3 just blows them out of the water entirely (at least in my opinion). The story and gameplay is just light years ahead in part 3.
As for translation, Scenario 1 is in english, so you can get the english copy and play that on your PC/Saturn, then get the Japanese Scenario 2 and 3 with a translation patch to play on Emulator or hacked Saturn (I would go with SSF emulator, it works easily and doesn't require any hacking/damage to the console). Don't forget that saves tranfer across games and affect things, so try to do it all on the same platform if possible.
And yes, the games are quite long, each one would take at least 20-30 hours I would say, but it's completely worth it.