Ah, I love ser and estar. Ser in the preterite tense is my faveee ^_^ [how sad is that]. It's only topped by the noun "Alcazar", which means Fortress.
Anyway, I'm picking up some grammar and vocab books from my ex-head of Sixth Form tomorrow so I can begin teaching myself Portuguese. And, I'm taking the same approach. Cram grammar like mad. The vocabulary will be the slower bit.
The only thing I'll find hard will be the accent, because Portuguese sounds nothing like Spanish at all. Looks similar, sounds more like Russian, so I suppose the pronunciation will be the longest part of this.