Winning or losing doesn't really matter much to me. I play for fun, and nothing you can say will change that. Sure, I have a low K/D, sure, I have a low rank in Halo 3, but I really don't care. It's not like it actually means anything. It's a number. And for the record, opinion and fact are two completely different things.
You have to go through the city and find audio logs to unlock caches. Once you unlock a certain amount, a cache will open. The more you find, the more caches will open. I'm not sure how many caches there are, but there are a total of 30 audio logs.
Also, Segeant Johnson should be a card with his face on it, with a code on the back near the bottom, which you can redeem on Xbox LIVE.
NOTE: If you look closely, you will find an easter egg in my post containing guides to find the audio logs. I won't tell you where though.