From the trailhead, follow the signs to the start of the North Boundary Trail. Take the North Boundary Trail north for 0.7 miles to the saddle between Sheep Mountain to the west and Point 8672 to the east.
From the saddle, leave the trail and head uphill to the west into the forest. For the first 0.9 miles or so, the forest is relatively sparse and the grade is relatively gentle. I found walking through this section to be very enjoyable.
After about 0.6 miles or so, you will reach a small highpoint on Sheep Mountain's east ridge. A view of Mummy Mountain to the northwest is available here. Soak it in; it is one of the only views of other summits that you will get. You can see the round summit of Sheep Mountain to the west from here as well.
At about 9250 feet, the ridge's steepness increases. Also, fallen trees make progress more difficult. It isn't too bad, however, and when you reach 9750 feet you will be on the "summit bulge".
Once on the summit plateau, finding the true summit point is a bit challenging. Use of an altimeter (and/or GPS) is useful. I found a "summit cairn" about 50 feet lower and 0.1 miles east of the true summit. The true summit had a larger summit cairn. The cairn looks kind of funny, sitting on the floor of the forest, imperceptibly higher than the ground around it.