Been along time

I just recently started trying to use Cubase 7, before that I was using Cubasis with Sound Fonts etc many moons ago. I can’t quite figure it out. Back then after recording a track in midi you could simply change the midi instrument with a click. Please correct me if I’m wrong but it looks as if this is no longer the case and that midi is only used now to control VST instruments and that any midi instruments are a dead notion.

I only ask as I’ve been trying to resurrect some songs from those days and can’t get anything to work. It looks as if you can only assign a midi instrument to a track on its creation and can’t alter it after the fact, It doesn’t seem right so could someone in the know please advise me on this.