You probably don't need a permit to put a garage door on the existing carport (assuming it was installed with council approval) but I would call the local council just in case there are any local planning, heritage, or visibility regulations. If not, you can get a quote directly from a garage door installer. It is likely going to cost you a lot more to alter & extend the existing carport roof "slightly forward". An extension is highly likely to need council approval if there are block coverage regulations i.e. what % of your block can be covered by structures. A reputable carport installation company should be able to design and provide extension plans for council approval. You don't need an architect. For a new door, you will need at least 150mm of side-room on each side of the opening for the door tracks to be bolted to. A 150mm infill jamb is definitely required on the house side. Your photo didn't show the boundary side of the carport but likewise 150mm will be required. For a sectional/panel type garage door, you will need a clear 200-250mm (depending on the manufacturer) minimum headroom from the top of the carport opening to the lowest point of the roof structure i.e. check for lights, rafters, and steel beams on each side of the carport up to 3m into the carport. The motor will require a powerpoint on the roof that is at least 3.5m into the carport and at least 350mm offset from the centre of the carport opening. Then you will need to decide on the colour and style of the panels.

I think it's very feasible and one of the easiest ways to get extra space. Your local Council's planning staff will generally pop out to your site and give you an idea straight away of what they'll accept. Give them a call (phone better than email).

You say you want stain ideas for garage door. This seems unusual, because usually garage doors are not painted, they come in a colour made in a factory. Do you just mean colours. I would suggest Dulux beige royal for render. Colorbond Evening haze for garage door. Then a cedar stain for front door. Or the front door could be any colour really. Maybe Evening haze to match garage door, or even a red front door.

Ok so Queenslands rules are a bit harder to find but it does appear that you’ll need to discuss the work you’re proposing with a Licensed Private Building Certifier. With a building permit the likely outcome. Some Qland Councils also issue building permits but this may not be your Council. https://www.legislation.qld.gov.au/view/html/inforce/current/sl-2021-0126