Learning Spanish,how good will I understand written Italian?

Hi,

at the moment I have an (I guess) average knowledge of English and only some basic French. My goal is being able to read written Spanish and Italian, as I often buy collectibles on eBay (mostly com/de - but also es/fr/it) and sometimes on mercadolibre (a South-American version of eBay). So I recently started reading a "Spanish in 30 days" language course.

Yesterday I tried to read some Spanish and an Italian item descriptions and although I'm only on Day 7 of the language course, I also began to unterstand some of the Italian description, as the word order and the vocabulary seemed very similar to what I already learned in Spanish.

So my question is:
If I finalize the course, how much will Spanish help me to understand written Italian? And what's with Portuguese?
And how easy is it to upgrade to Italian then?

Michael

My experience is the other way around, but I hope it helps anyway. Having studied French, made it really easy for me to study Italian. Having studied both French and Italian, but no Spanish at all, I can say I can easily understand most of written Spanish, and if I am focused, spoken Spanish too (provided it is not spoken at a super fast speed). Portuguese is a bit harder for me to grasp. I would say that, as far as passive knowledge is concerned, Romance languages can be mutually intelligible to a high point. Now, producing speech is a whole different issue...