If it's not too late, I reccommend that you get your money back on the cadence meter. This is really a tool for advanced training. New and intermediate riders are unlikely to benefit much. You can always count your cadence with a watch if you think it will help. but for the vast majority of cyclists there are only three cadences: Too fast, too slow, and about right.

Try not to worry too much about your shifting and cadence. It won't tbe very long before they are problem-free and totally natural. By the end of your 28 mile ride, I bet you will have it down pat.