Hi Peter,
You can filter event listings by using the category attribute with a shortcode. Like this:
[events_list category="1"]
There’s more on shortcodes here:
http://wp-events-plugin.com/documentation/shortcodes/
There are a couple of ways to add fields to the registration / booking forms, the easiest is to use the built-in Forms Editor, which lets you add pre-built forms elements to the registration and booking forms.
It’s also possible to hook these up to the standard WordPress profile page / settings, or with BuddyPress, if needed.
You can also edit templates directly.
Let us know if you need more specific examples.