Saves can be backed up, but restored only to the cartridge that it is from. Editing is not possible due to encryption. Newer games have more advanced encryption.
http://3dbrew.org/wiki/Savegames
Saves from the Gateway MIGHT be transferable to other Gateways, though.
http://3dbrew.org/wiki/Savegames
Saves from the Gateway MIGHT be transferable to other Gateways, though.