Hi Adam,
Glad to see you reading/posting here before going to buy the tank. I did the same and was glad I did when I discovered the existence and importance of cycling etc!
As everyone else said, the pinned topics are the place to start.
The Rekord 120 should be fine for a beginner. I bought the Rekord 70, simply because it's all I have the space for, but I do wish I had space for at least another school. The Juwels are not the cheapest way to setup, but they are certainly the more convenient way, with the built in heater and filter and matching stands.
As for other stuff you would need:
Substrate (gravel/sand)
Thermometer
Dechlorinator
Water test kit (ammonia, nitrite, nitrate, pH, etc)
Optional live/fake plants, ornaments, caves etc (depending on the fish some plants/caves might be important)
Net
Possibly a magnet glass cleaner
Large bucket (for water changes)
Siphon
Range of food for the fish you choose (bloodworms, flakes, etc, etc)
That's all that springs to mind at the moment...since it hasn't been that long since I was making this list for my own tank.
Good luck