I was going to refer you to the Snooping and Jealousy board, but I see you've already posted there.
We're not ones to ask for snooping advice, but we can help you with relationship advice.
Um, I am not exactly that naive, however, statistically more divorces are due to financial issues than cheating.
The bottom line is, if we "lost that loving feeling" and trust, it is time to go.
"Trying to help out a friend" is very likely to get you in legal trouble.
I'm a systems administrator and I get inovlved in this stuff, unfortunately, more often than I would like. Don't do this.