I can give you the basiscs, there's just one part I don't know how to do. The variable input file - I'm sure there's a 'wildcard' you can use, but I don't know what it is.
So you'll need to edit your crontab file. Log into ssh and type "crontab -e". That will open up the default text editor (nano/pico). Now your crontab entry should look something like:
- 1,2,3,4,5,6,7 mv /home/user/path/to/file/origional.xml /home/user/path/to/new/podcast.xml
that all needs to appear on one line, without breaks. There need to be a space between each * . that part tells how frequently to run this command - this one is running once a day, 7 days a week. Check out the K-base on crontabs for more explination of the time thing.
You might be able to use *.xml as your wild card - just be sure there's only one xml file in the directory to begin with, or it will combine them. You can allways test the command to see if it's working. Just type the part from "mv" on.
Hope this helps