Build a google form using App Script and forward information to google sheets and prepare packing slip

I would like to design a form using Google App Script that sends information to a google sheet and generates a packing slip that gets sent to the user.

I have a sample script and form that can be used as a base to achieve the results but the following are the conditions:
* The script must have validation for example to validate if the contents of a specific cell is a number.
* The form should have an intro to explain the process and a thank you page that summarizes what happens after the use submits the information
* A mock up is provided using Microsoft Excel Forms and VBA. This is for illustration purposes only but will be a great asset in understanding what we want to achieve
* The form can be similteanously used by several users (usually 1-6 at a time)
* Some fields appear or disappear (get disabled or enabled) depending on a choice from a drop down.
* If there is a viable alternative to Google Apps Script/Google Sheet, I am open to suggestions.
* The script should be easy to modify (not encorded) in case I want to rename columns. The beautiy of using Web App Script is the ability to use HTML to control where every thing is placed.