I'm a huge fan of Ragnarok Online and played when it first came out, me and my wife both played it for a while. When I saw ToS I was immediately attracted to it because it reminded me of RO. I was a bit disappointed because I missed CBT signups and etc.
Is there still anyway to signup to play the game before release?
It's worth noting that there may be changes to the shop between International and Korea. International is self publish, Korea is Nexon and has very similar prices and style to Nexon's other Korean F2P titles. approach this as a new game and enjoy the artwork/music.
the class progression is kinda complex so plan your build accordingly. you can use http://www.tosbase.com/tools/skill-simulator/ the most updated ToS class simulator. despite there being skill reset scrolls. You cannot undo the classes you have choosen. you might also want to ask a 2nd opinion in the official forums as there are user there that play on the korean server.