[Campeador]

Clarification:
The "Star Blazers: The Quest for Iscandar" story was divided in two parts, Campaign 1 and Campaign 2.

The first part: StarBlazers-Campaign1_v1.1 (6.3MB) (updated 9/29/05)
and the music file: StarBlazers-Music1.rar (24MB)

The second part: StarBlazers-Campaign2.rar (16MB)
The "Campaign 2" file looks much bigger than the previous one, and it is, since there are a lot of new pics (used for story telling) and one music file. It also uses the same ships from the first part in addition of the new ships.

So, to answer the question, they are not combined, and it does not replace the first campaign. The second campaign is the continuation and conclusion of the story. If this is the first time you try the Mod then download the 2 campaigns and the music, that will be 3 files to download combined.
If you already have the "Campaign 1" and the music from before, then just download the "Campaign 2".

I hope that this explanation helps.

note: I went back and edited the post on the campaign download page to make it more clear also.