New to 3D printing. Want to make functional parts for business

I repair old telephones. (Not cell phones) I have played a little with 3d printers over the years... just a tiny bit. I do have 2 laser engravers and often make flat parts with them. I am looking into the possibility for making more intricate replacement parts such as battery covers on older cordless phones, antenna housings (empty semi-flexible plastic tube) maybe even button caps (white plastic caps with black dial pad numbers, tiny power switch plastic slider, etc...

Basically I'm not interested in making toys. I need functional parts and I need them to look reasonably nice (not the typical texture from 3D parts pulled right out of the printer)

There are so many choices and thins to look at. I'm hoping someone can help narrow down the search or provide recommendations.

I don't need to print anything large. 6" bed would be fine.

Also, what is the easiest way to replicate a part like a battery cover door? Is there a cheap and easy 3D scanning that works? Or is there a reasonably priced service where I can send out a part and get back files??

Thanks

Fastest and easiest and most accurate way to replicate small parts - is cad and a set of digital calipers.

Unless you want to spend serious money on a scanner.
This is probably the cheapest one worth having: https://www.scaninabox.com/
And that's an entry level machine - so you'd most likely still need to spend a fair amount of time fine tuning the scan.
Basically nothing short of an industrial entry level scanner at around the £10,000 mark will do what you want and even then there are always going to be issues.
Unfortunately the 3d scanning marjet has yet to produce high quality at cheap prices.
Cheap decent printers - no problem at all.
But cad and calipers are still your best friend for reverse engineering.

As far as tiny functional parts goes.
2 options. use a very small nozzle diameter on fdm - 0.25-0.15
Or go resin based. Which while very clean and high detail does come with it's own issues.

As far as sending parts and getting back files goes - I can do that, no problem :-)

Also there are commercial scanning services - averaging around £100 for a single scanned part.

I'm a lot cheaper - though it obviously depends on the size and complexity of the thing to be replicated and whether you want a perfect replica or something that fits but is actually designed for 3d printing.
Bear in mind everything you want to copy has been injection moulded - whole different kettle of cephalopods !