I had the same exact problem, and here's what I did.  When I would go to fly a lesson, I would go to the volume control in 'Options/Settings/Sounds' and I turned everything but the 'Lessons/Flights' bar almost all the way down, and then turned the 'Lessons/Flights' bar all the way up.  That way, you can hear what Rod says clearly and still be able to hear the environment.  Works pretty good.

BTW, I wouldn't recomend trying too hard to get any of the checkrides done.  Not very many people can get them, and some just can't do it at all (this is because of a bug in some versions of the software, not because of skill), so if you run into problems trying to get your Private Pilots License, don't beat yourself up over it.