CycloDS's save files are editable [rather easily] by pokesav.
You can also use the 3in1 tool to dump / restore a save from a retail cart as well. The caveat here is Heart Gold/Soul Silver. Due to the RF transmitter, there isn't an easy way to get save files off those two retail carts.
To use the CycloDS's cheat functions, you have to using the flashcart to play the game [which isn't bad, the CycloDS has some really nice compatibility]. You can dump the retail to the flashcart also using the 3in1 tool [again if you have a 3in1]. However, you're really better served looking at Cyclo's forum and such for explanation of those processes.
You'll need to get a 3in1 as well I believe if you want to take a retail cart save and manipulate it. Also you're going to see a microSD reader for your computer, not really too bad but it's something to remember you need. Although, the 3in1 does have a tool to ftp it wirelessly, I really did not like using it [and it destroys the battery life even more].
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Quick add edit. If you have a DSi, CycloDS won't work. I don't know diddly about the DSi solutions. Also. If you have a DS fat, it will prolly be difficult to find a full-size 3in1.