Script to monitor/report on changes to large files

Need the following script made w/ appropriate front-end. 1. Setup cron to receive 300MB file (these are big files) from an ftp server 2X per day (every 12 hours) on to my server 2. Unpack and extract the compressed file and load its contents into a database 3. Compare contents of most recently downloaded file with last file download 12 hours ago and note changes between two files. 4. Develop a script so I can isolate rows of changed data I am interested in. I should be able to add more parameters to monitor the changes for between the latest downloaded file and the file downloaded 12 hours ago. 5. Create script to email me latest changes every 12 hours or view directly from web interface. This is about it for now. If you can work with very large files quickly, and are good at data mining/extracting large amounts of data, there will be additional work.