The trailhead as shown here is accessed from the highway rest area, which wasn't immediately apparent to me. I'd suggest parking as soon as you find a spot as it begins near the rest area entrance. There is also a trailhead across Route 30 from the overlook but there doesn't seem to be much for parking up there. At that point there is currently a sign posted stating the trail is closed for maintenance. I proceeded with caution, and there is no sign of any maintenance to the top of Marsh Hill, making for a nice (albeit short) hike in itself. There's very little info on the rest of this loop - below is the best I could find after the visit. There is work being done on/near the last 3/4mi so I would suggest not taking the trail beyond Marsh Hill if traveling counterclockwise. Beautiful terrain with some nice views of the gorge.

https://www.oregonhikers.org/field_guide/Memaloose_Hills_Hike