Yeah, the firmware is up to date. How do I know which file to download? This is as far as I got before I started getting confused:
If it still has the original D-Link firmware from the factory, you need the factory-to-ddwrt-firmware one I assume. It even says special image for initial flashing. Then after that I'm not sure if that's all or if you need the other one as well.
I've never flashed DD-WRT onto a d-link before, but with the Linksys WRT54GL you first needed a so called "mini" version of DD-WRT because the original firmware only allowed firmware updates to be 2MB in size while the regular DD-WRT is 4MB. Flashing it with the 4MB one would cause the router to brick itself. After you put the mini version on there though, you could apply the full 4MB version if you wanted or you could just use the mini version since it has all the important things anyway. I assume this factory-to-ddwrt firmware is the same as the mini version, but I don't know because this factory-to-ddwrt file is bigger in size than the regular one...
But it's probably pretty safe to assume that the factory-to-ddwrt one is the one you want, going by the description.