Altering core plugin code’s generally not a good idea, but you can safely override and customize any of our templates – please see the initial section of our Themer’s Guide for more details on this:
https://theeventscalendar.com/support/documentation/events-calendar-themers-guide/
The basic process is pretty easy and in this case you’d grab the ticket form (from plugins/wootickets/views/wootickets/tickets.php) and set it up in your theme (ie, at themes/twentyfourteen/tribe-events/wootickets/tickets.php).
I hope that clarifies things 🙂