Looking for advice help with cutting open a whole in an exterior wall in order to install a new door. My project is to close one door up and install a new one on the other side of a window.

Here are images from the inside then out.

My thoughts are either to buy/rent a AllSaw AS170

or renting a concrete chain saw like these

and just cut the opening out and take it from there.

Is there anything wrong in my thinking or advise/tips you could give? I'm guessing I need to install a lintel for something like this? And should I worry about the door being so close to the corner of the house?

Any insite would be greatly appreciated.