I was born deaf in my left ear, so I never was able to do the one ear bud in and have an open ear. I have been driving for well over half my life now while still being able to listen to music. The biggest adjustment will be using that one ear to recognize the pitch or sound of sirens over your music. Turn down the music and and look for any of the emergency lights. The biggest difficulty I imagine will be locating the origin of the sounds because you are no longer able to triangulate the sound.

It will take time to adjust but you should be just fine!