I was planning to take the DipTrans through IOL but have read that this is only recognised within the UK. I have no intentions off living in the UK so am unsure if this exam will help me.
It will help as much as passing the ATA, ITI or NAATI exams for certification. If English is your mother language or one of your source languages, it will be understandable anywhere around the world if you opt for CIoL or one of these.
I have also read that to become a successful translator you need to have a 'speciality' like medical or technical. Is this right and if so how do you go about getting a speciallity?
The best way is getting experience in a particular field. It helps to try translating in a few to see the fields that interest you, and to work your way from there. Several institutions offer a package, but those may not necessarily reflect where you'll be ten years from now.
Specialization is neither a requirement nor a guarantee for success, but it is true that successful translators tend to specialize (can you follow that logic?) What I mean is, that specialization is often decided once a certain degree of field experience has demonstrated that a translator is exceptionally better at certain things than at others. In some cases, the inverse is also true: an engineer may only want to translate subjects in his field, for instance.
One last question, I want to do an MA in Translation. Do you think this is neccesary to become a translator? Do you know any Spanish Universities where I could study this Spanish - English?
It may increasingly become necessary. Where once before there were only a handful of translation schools and translators usually came from linguistics or related fields, there are now many institutions offering translation on the undergraduate or MA level. This is not to say an MA is sine qua non, but it will help.
Spanish universities tend to be oriented towards the inverse (into-Spanish) combinations. A few, like the UAB, have native English staff who impart inverse courses, and several others like the UCM come to form part of exchange programs with the EU that enable them to have visiting professors from foreign institutions. Whatever language combination you may be interested in, the core theory course(s) will have the same content and lie at the heart of the curriculum. If you hold a BA Spanish degree, it may just be as interesting to take up one or two inverse courses to see how theory is applied, and take it from there.
I suggest you get further information from the Instituto Cervantes nearest to you. They would also be informed and aware of any scholarship options.
Spencer also mentions something true; in taking an MA, experience gives you an advantage.