Hi Vidette,
You should check out the sample Timecard form that comes with InfoPath - it is likely all you will need in order to collect the information you are looking for. I don't have a lot of experience with digital signature, so I'll have to let someone else answer that, but as for the last question, there are a lot of ways to solve this problem. Here are the ones I came up with:
1. Write a SharePoint event handler to watch for timecard uploads and then shred them to a text file
2. Write a command line utility that you can run manually or with a scheduled task to pull all the XML files, parse them, and then shred them to a text file
3. Use our Database Accelerator to shred each form straight into the SQL database as it is submitted.
The third option, of course, is how I would do. Not only do you get codeless shredding with the DBXL webservice, but there are also a slew of other features such as version tracking, fine-grained permissions, indexing, and many others! Try it out here:
http://www.qdabra.com/proddetail.asp?prod=QDBXL1
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge