RE: Where are store the CustomerPage (newTicket.html)
Inside SO_SERVICE (I am guessing that Service is installed here), there is a folder called "templates". Underneath this folder, there are several folders containing the customer page templates, and you will find a "customer" folder inside each of them.
Inside here again you will find "newTicket.html".
But note that changing that file directly is the old method of doing this.
If the customization is done through the Service appliaction (the UI), then the changes are stored in the database instead (which overrides whatever is in the files on disk).
You can see this inside Service:

All marked as "Yes" under modified are modified using the new method. I recommend using the new method anyway to prevent replacing the customer templates after an upgrade.