I filled in all that was applicable. ...in english language section i wrote "english proof attached" as my husband gave school cert for English requirement last time. I did attach my ielts from last time. I guess there is no harm in attaching all docs that we think could be asked.
And my husband calculated the cost from the immi site...it came around $600+ for him i and our daughter (2years) and we gave our credit card details for it. I did get acknowledgement for the mail but not for the visa yet so i ll wait then give them a call to ask for the details. Hope it helps.