Hola. Bienvenida al foro. There aren't really all that many differences between the way people pronounce Spanish in Spain and the way they do so in Latin America. The main ones are with the letters z and c In Latin America,* z* is pronounced just like an *s* (as in *send*), whereas in Spain, it's pronounced like the *th* in *thin*. In Latin America, when the letter c comes before an i or an e, it's pronounced like an s, whereas in Spain, it's pronounced like the th in thin.
One other difference between the Spanish in Spain and that in Latin America is the use in Spain of "vosotros" when addressing more than one person informally (i.e., it's the plural equivalent of "tú"). The two programs I know best for learning Spanish--Rocket Spanish and Learning Spanish Like Crazy--focus on Latin American Spanish and thus ignore "vosotros." However, if you expect a lot of your conversation to be with people from Spain, you may want to make an effort to learn how to conjugate verbs with vosotros.
As for "quiero," it really means "I want," and so it's more direct/abrupt than "quisiera," which means "I would like." Even in Latin America, if you're trying to be polite, you might be safer with "quisiera." In general, however, both in Spain and in Latin America, people tend to be increasingly informal. Also, as an obvious non-native speaker, you'll probably find that people will overlook things they wouldn't overlook from a native speaker.
Finally, in addition to Rocket Spanish, you may want to listen to some Spanish spoken with the accent from Spain. I'd recommend the podcast *Notes in Spanish* at *__http://www.notesinspanish.com/__*. The podcasts and the forum are free; if you'd like transcripts of the podcasts that include some lessons and tips on usage, you can get those if you pay.