A modem and swaret (especially the first time use) is not a good combination.....
The other two links I gave should give you what you want. Especially the first one, it shows the 'default' slackware packages for a specific version and the current version of the software.
You could also write a little script that uses wget/ftp/scp and one of the latest filelist for the current slackware packages.
ftp://dl.xs4all.nl/pub/mirror/slackw...t/FILELIST.TXT
This is also something your friend should not do using a modem
Hope this helps.