Altering upcoming events layout

I’m working on an events list for my club here: http://woodend.ubisan.com

I’ve got an upcoming events widget in the sidebar. I want the date to be listed, then the event title and then the time. Any idea which files I should edit to do this and how to make sure upgrades don’t overwrite?

I also want the event time to show properly. At present it only shows 12:00 even when another time is put in.

https://wordpress.org/plugins/spider-event-calendar/