Modding your DS, huh?
Actually, you don't need to solder any kind of chip in your Nintento DS to run homebrew software or play backup games. You can simply get any of the SLOT-1 or SLOT-2 devices and plug them in to flash the software in your DS.
A few of the popular ones are the R4 DS, M3 DS Simply, the TT DS and the more expensive Edge. As you can see, not such original names :)
If you see any SLOT-2 devices (the GBA slot using kind), these are kind of old fashioned. Get a SLOT-1 ones, they are cheaper and easier to use. Read more about this at Wikipedia.
FlashMe is by far the most popular tool which is used to run software on your DS. It is a piece of software that is 'burned' into your DS so it runs every time you turn on your DS. When run, it allows you to run any kind of game or program plugged into your DS (in the normal SLOT-2).
Easy, right!? Get one of the products by following one of the ads above or below. Enjoy your DS! :)