Logistics of disembarcation Buenos Aires

We will be finishing a cruise to SA in BA. The boat will spend the last two nights docked in BA.

I would like to take an early flight to El Calafate and therefore would have to disembark around 5 am.

If I disembark with the normal disembarcation, it will be much later, and essentially will lose a big part of day 1 in Patagonia and would have to restructure part of the trip i.e. going to El Chalton when landing

How does it work with customs in BA off a cruise ship?

Also does anyone know if taxis are available at the port that early in am as this cruise has the overnight in BA

We will actually spending the previous day in BA and ? already have cleared customs entry

We will have entered Argentina prior in another port, but then go to Uruguay and back again to Arentina

Thanks

Sandy