Well, it's as I told you. It's a bit difficult, but not impossible. You have to solder 4 wires and one of them is the complicated one. It's a very small point, and it has 2 possible alternatives: underneath the cartridge slot or on the back of the board. I picked the second option because it seemed safer.
Basically all you need is a soldering iron, thin wires, thin solder (I used 0.5mm) and flux for cleaning the board. Some people solder the wires to a microSD to SD adapter and then connect it to a card reader, others (like me) solder the wires directly to a microSD reader and link that to a PC via a USB connection.