It's a steep hike up, but an easy hike along the ridge. You can start from two ends, or pick it up from the south, but I haven't been to the southern starting point. There is a white plactic ribbon marking the entire trail, as well as the usual group hiking ribbons.
The container is a small, clear tupperwear container with a Sponge Bob signature book. Lots of goodies in there. It's just off the trail, but still in sight of other people if not careful.
This is an easy drive from Humphreys, Cheonan, or Asan. Asan has a hot spring, and public foot bath where the hot springs are piped to the surface and definitely worth a visit. Look for geocache which will take you there.