that 3d sh!t appears after I click to proceed the payment.. but not all cards has this(that says a lil box) and I have to introduce the DNI-NIE(I don't know how it's in english) and a password to give authorization for the payment.
Normally that 3D secure system should ask you a password and it's one you have created yourself.
However, if it is your first time coming across that system (which is widely used now) it should ask you to create a password.
Well that's my understanding of it. It should not be too much of an obstacle for you as the card owner but helps to prevent fraudulent payments on our site (by people who are trying to use someone else's card details they found somewhere else).
I purchased S1, upgraded to S2, and upgraded my friend to S2 all with paypal. It wasn't as instantaneous as credit card. I did it at work, and 3 hours later, was home racing with my newly acquired licenses. I do believe it only took a few minutes though, definitely less than an hour, but it does state it could take up to 24 hours on the site I thought.
The 3 hour lag for me was due to purchasing, then waiting until I got home from work to check on it's status.
Nowadays it doesn't really matter what license you have. With the S1 license you can join any server that is running an S1 track with S1 cars. You'll just be kicked if it changes to S2 content.