Trigger an IDoc based on conditions

Hi,

I'm not a technical guy, but want to understand below to confirm a solution.  Please suggest possible solutions on these two.

1. I have a requirement to trigger an IDoc when Sales Order custom fields values changed.

2. I also want to generate an IDoc when a Sales Order created.  That should not be repeated again. 

How to design these two?  Please suggest.

Thanks in advance.

Sekhar