Don't waste money on expensive parts, although having a professional could be a good idea.
I getho'ed mine since I have no money and and nobody nearby, I did everything for like 20 bucks.
All you need is a hot Iron kit and some very thin cables that you can rip off any electronic you don't need
I made a hole on the slot where the stylus goes since it's very thin plastic, using an exacto knife and just stuck
the cables out and welded them to a broken USB cable+SD card
After I got everything done, I cut off the cable where I welded (USB+SD Card) and fit the hard mod cables
inside the Stylus slot where nobody can see them, I just keep my stylus on my pocket lol
Sure having a Micro USB slot is nice but how many times are you going to use it after you Unbrick your 3DS?,
this method worked and it's cheap, and on a New 3DS nobody even notices the cables are there, but you
have to be extremely careful and it could be a pain in the ass if you don't weld properly.
Tin is cheap tough, so you can practice making small beads, they have to be small like
a rice grain. If you're a noob you tend to make a mess with tin, but you can heat it up and remove it
using a metal wire. Also working on the 3DS requires a TON of patience and delicacy, since every plug
is TINY and can break easily. If you have the patience of a saint and the delicacy of a butterfly you can do it,
it's not hard, just time consuming.