It really isn't hard to solder on the board, the main thing is that the wire you have to solder isn't isolated. You can't let it touch any capacitors or contacts. If you want to practice your soldering skills, try to buy the cheapest ps controllers on ebay ( I bought them for €1 each) and try to make another controller from it. I build a few arcade style controllers out of them.
Even if you don't build any thing from them, it's still a great practice.
I've started with those because my soldering skills were terrible then I went on to do the famicom av mod, then switchless snes mod. If you can do the snes mod, a gba is really easy to do. Just one wire on a capacitor, but if you don't want full backlight (the second light option )
You don't even need to solder.