Sorry for being such a "noob"... but I still don't find any *.pk3 file when unzipping. Instead, I find several folders with files. The folders are: gfx, levelshots, maps, scripts, sound, textures, video and a "readme.txt" file. What am I missing here?
Apparently, my system was downloading this as "tundra_rush_beta.pk3.zip". Consequently, I unzipped it and found the folders previously reported. On a hunch, I renamed it WITHOUT the .zip and saved it accordingly. That was the trick! Thanks again for the help.