Hi there,
It depends on different factors such your residential address at the time of lodge.
"how long it takes to come through"
It could take up to a year in some rare cases, but normally 4-5 months.
"do I have to wait until a specific time for the ceremony"
No, your local council will send an invitation letter, though you may contact them and ask them to change to a different time.
"how much does it cost"
I think it costs about 250
you can find all the information here.
http://www.citizenship.gov.au
Cheers