Hi
Regarding your Curriculum Vitae, it is ok to have 2 pages do not worry to mych about that try to mage it as simple as possible for more info and help try searching Google for Eures is the European Union Type of CV so it will help you very much you just fill the spaces and the cv is ready you just hav eto save it. I did that for my own CV and it went fine.
As for your appearance try to look as profesional as you can, that is business suit and pants usualy people chose black or blue, simple shoes, nice shirt with tie, fresh shave and fresc hair cut, and do not forget always smile. And be cool do not get nervous it will show, in that case just excuse your self and give the emotions reason.
I do not know how many will come up at the asesment day but it can varry from 10 or 20 to probably 100 it really depends on the location and on many other factors.
Read my posts you will find all the info you need!!
Regards