advice on red tape re changing external windows in apartment

I just bought an apartment in St Kilda a couple of months ago. I am planning to do extensive renovations but the first thing I want to do is the change the external windows - they are not double blazed, they are 40 years old, they leak wind and let in traffic noise from the street that keeps me wide awake at night and the aluminium frames look old and don't slide (vertically) well.

I want to replace the whole window structure including frames with double glazed, horizontal sliding windows with bigger glass (so less frames). The entire area involved is around 8 metres in each direction around a corner of the apartment by 1.7 metres in height.

I see that some units in my building already had similar things done.

My question is, do I need to get a council permit for this? Do I need to get body corporate permission for this? If so, do I need to engage an architect or engineer to produce some technical drawings on the new double glazed window system I want to put in? Can a glacier/installer produce such drawings? If body corporate needs to approve, is this something that gets discussed at one of those monthly or quarterly meetings or is this something that I can put forward at any time and people will vote on it straight away sort of thing? Or is it like a notice will get posted in the loby area and anyone who objects can object until time expires sort of thing?

Thanks in advance.

Jin