Spoiler
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"spot" - (1d20+4)[7]
"listen" - (1d20+4)[17]

For rolling, I don't have a strong preference. I have some rules of thumb for when I'm DMing and I tend to stick to those:
Player rolls if (1) they are actively doing something or (2) they are making a saving throw. DM rolls for passive effects (like elves finding secret doors, there is no spoiler alert quite like "Ok, all the elves in the party, roll for secret doors")

Until I edit my signature, here is the link
http://coyotecode.net/profiler/view.php?id=15406