Good I am glad you are getting the hang of it.
You can submit your data back to the DB, with the stock InfoPath form. If you take your data fields and put them in a repeating table you will have the ability to insery new rows.
You may want to check out the Database Accelerator. Qdabra Database Accelerator Suite Version 2.1.2808 - Developer
It includes a bunch of web services so that you can interact with multiple tables, active directory, etc. If you are going to be creating InfoPath front ends to your backend data then I think it saves a lot of time and gives you a lot more features.
Let me know if you have any more questions.