Joe,
Regarding the GAPAN test, the only source of reliable information for any specific questions will be from GAPAN themselves. I would contact them directly. GAPAN's web address is
www.gapan.org.
As for qualifications, the only thing anybody really takes any notice of these days is a degree and, unless you want to be a fashion guru, a science/maths based one. Having a maths or science A level amongst other things always looks good too.
However, as with anything else, get the information direct; from your preferred employer(s) in this case. I strongly advise that you don't make plans or rest on assumptions born from hearsay.