No one can ever truly be ready. Just do what you can now, especially with your health and fitness. Don't have to kill yourself, just do things like walking a lil extra and cutting out all sugary drinks. As much as I hate to say it, cause it is NOT a substitute for teaching, you can always find good videos on land nav and FA on youtube. Get training where you can to get an edge, just remember that you aren't the first or only one to be in your situation.