Change SSL Certificate that ISPConfig uses to a paid SSL

Hi all, is there a way of changing the SSL Certificate that ISPConfig uses as default (Let's encript) to one that i can buy and add for the server to use? It's a bit uncomfortable for clients to have the "your connection is not private" popping up.
Also, is there a way of accessing ISPConfig server without the need to specify the port 8080 at the end of the url? This is more for the clients.