We have a JP at my work so its not a problem to get it all certified before I send it in. Should I get the whole lot certified?

The docs I have are

Higher School Certificate
HSC Transcipt
Statement of Attainment from the ACCM
Attendence certificates for two courses
Marriage Certificate

Also, if I include a self addressed, stamped envelope will they just assume that I want them to send me a confirmation of receipt?
Get it all certified just to be sure. I would not assume that if you include an envelope that they would automatically send you a receipt. Receipt letters are usually automatically generated and mailed out. HTH.