Utilizing/ Converting another database with craft
Welcome to Craft! Craft does not require coding experience to set up fields and relationships (attendees to events, for example). All of that is handled from the control panel. 

Displaying the fields on the frontend requires some knowledge of Twig, the templating engine Craft uses.

Transferring the data may require some pretty heavy coding, depending on how the data is currently structured. There are a few importing plugins (here's a popular one) that might be able to help. From your numbers above, migrating by hand may not be an option, so you might need to invest in some research or hire a developer to help with that phase.

Craft has a lot to offer out of the box in terms of organizing content. I could see you making use out of singles and structures to manage events, hotels, attendees, etc. I recommend reading through the introduction documentation to get a hold on how Craft is set up.