Hello Patrick,

It seems you have already purchased, and a Pro ticket is already in process so that i help you to customize

I will just answered here for this (as we will see all custom css in pro ticket) :

Hello,
We have been testing the free version and really like iCagenda!
My question is if we buy the Pro version what will happen when it's installed?
Will it wipe our current setup and events?

Thanks!

When a free version is installed, and you want to upgrade to Pro, just install the Pro version with Joomla Extensions manager (as for first install of free version) and iCagenda Pro will automatically update the free to pro, and keep your data with nothing removed!
Of course, never uninstall iCagenda or you will lose data!
Installing the pro will process as an update, so no worry to have about!

Best Regards,
Cyril