On playing DS games. I do indeed know about such things and use it myself to this day, though as a legacy thing rather than a real thing.
You patch games with EZ4client, boot in DS mode (flashme, nopass, whatever else you might have to make it happen), run game. Some ROM hacks, cheats unless you go DSATM and other such fun features are not going to happen.
Last patch update for EZ4client was early April 2009, anything much beyond about May 2009 (numbers will vary between lists but about 3600, if you don't have a preferred database of such things then
http://www.advanscene.com/ is good stuff) then will likely not work.
If you have a SDHC supporting DS slot cart it is almost certain to be better. Best to save the EZ4 for GBA purposes.
Looking at the thread you made when seeking one you probably got one of the last ones when there were very rare and hard to come by. To that end it should support DS mode, and even if not then it should not brick it (it was the really new models I am unsure about).
I forgot to also mention. If you have or have access to a hacked 3ds then you can dump games and saves easily with that, even more so than this.
I should also say said DS mode dumpers will not support SDHC like some of the newer kernels do for games. Depending upon how much you have loaded your memory card up and what size it is (those 2 gig miniSDs are not so common) then if dumping games you could find yourself having some fun shuffling files around to make space.