The USB-C port/board are included in the price. Return shipping is also included in the price.
Most consoles it’s $50 for the install. Some it’s more as they require special boards or more labor.
In regard to the *DS consoles/clam-shell consoles
These installs have the risk of the console dying because of the ribbon cables that go to the top half of the system crack with age. This is the same risk you have when you just use the console. This is a fault of Nintendo so it wont be something I repair/refund if it happens. The USB-C port will still be installed and checked to make sure it is working. If it does happen you’ll need to find someone to replace the parts for you as it isn’t something I do as it’s annoying as fuck, I will however cover the shipping to the person doing the work for you(inside the us/canada) though. There have been a lot of people on discord with this issue happening to them on the 3DS systems. So I figured it was worth mentioning.
I got a USB-C port install on my New 3DS and it could not have been a better experience. Customer support is great, got back to me very fast about any questions I had. Super clean install, almost looks stock. The dock pins still work as well. Shipped back to me way faster than I expected. Got a cool sticker and a keychain or something too 😛