Hello @MangBerto, welcome to PinoyAU! ๐
That's right, kung masipag kayong mag-research on your own, kaya naman mag-lodge ng application on your own. Tapos kung hindi kayo sigurado sa steps, pwedeng-pwede naman magtanong dito sa forum. HOWEVER, if you do decide to get an agent, make sure that the agent is registered in MARA (http://www.visabureau.com/australia/mara.aspx). Otherwise, possible na may maling details ang masabi sa inyo. (Kaya rin siguro iba-iba yung sinabi sa inyo nung dalawang agent na tinanungan niyo.)
Anyway, for a Pre-Primary School Teacher application, the AITSL requirements include the following:
<i>-Degree that is comparable to at least <b>four-years full-time higher education</b>
<b>45 days</b> of supervised teaching practice
IELTS Academic Version (at least <b>7.0 in Reading and Writing</b>, at least <b>8.0 in Speaking and Listening</b>)</i>
Source: http://www.aitsl.edu.au/assessment-for-migration
Do ask your wife if her MA degree satisfies all of those requirements, because if not, sayang yung AITSL application niyo. It doesn't matter kasi kahit 5 years of 10 years na ang teaching experience niya, importante sa kanila yung degree, for some reason.
After being assessed as suitable by AITSL, then you can sign-up for an Expression of Interest in SkillSelect. Once you have been invited, THEN you will finally be able to lodge your visa application.