Depending on the size of your door opening will depend on whether you need to temp prop the opening to remove the lintel bricks or not.
If the opening is 1m (3ft) or less, you won't need to use temp propping to support the brickwork above the lintel. If the opening is more than 3ft wide, you will need to remove a brick or two and install a small beam through the brickwall with props supporting the beam either side. Then remove all bricks from under the beam.
We have systems in OZ & the UK that you can place on top of an acrow prop (Adjustable steel prop) that is designed for these situations.
If the brick wall is to be rendered, I would leave the lintel bricks in place and only toothe in the side bricks for strength. Then brick up the opening to the underside of the half brick lintel.
If the bricks are a feature brick, then you will need to remove the lintel bricks and also toothe in your brickwork both sides of the opening. Brick in the opening the same brick coursing as the rest of your house.