Assuming you've arrived at Loch Lomond without losing your oil pan or damaging your vehicle too much, walk to the north end of the dam and locate a trail that heads uphill in a northward direction. The trail will cut through some willows, cross some rocky rubble and then continue north through some more willows before breaking out onto tundra/grass terrain. After 400 feet of gain, the trail will turn more to the west and begin the long trek toward the summit of James Peak. For a while, it hangs close to the south edge of the broad east ridge of James, offering views back down into the Loch and of the other higher lakes. Soon, the Continental Divide Trail will come in from the right. Continue westward for a while, still following close to the south edge of the ridge, enjoying the spectacular view. After a while, the CD trail will leave the edge of the ridge, head up the middle of the main east ridge and then wander over to the north edge of the same ridge offering nice views towards James Peak Lake. Finish out the ascent to the summit. The entire hike goes easily on Class 2 tundra terrain with some rocky sections, not of prolonged duration. The summit offers some enticing views of the Indian Peaks Wilderness and some of the summits farther north in Rocky Mountain National Park. Please note that our ascent of James Peak was our first 13er, and even pre-dated our completion of all the 14ers. We have done the best we can to update our information, but you would do well to check on other sites.
For the descent: This is the best part of our proposed route. This descent left a long-lasting impression on us. From the James Peak summit, head down the south ridge. The first third of a mile goes easily on mostly tundra, then the ridge begins to drop more seriously where you will begin to encounter more rocky sections that will require some maneuvering around to find the best way through, especially as you near the James-Bancroft saddle. The final drop to the saddle will be the most difficult part of this descent, along with the 400 ft. trip down the slope to Ice Lake. At Ice Lake, hiking around either the north or south side of the lake is not easy due to boulder talus, talus and rubble. We chose the south side and had to cross some significant boulder talus areas. Once you gain the east end of the lake, the terrain changes over to tundra.
As you begin the drop from Ice Lake to Ohman Lake, roughly follow the drainage. There will be rocky outcrops and tundra benches to work your way down. It's all part of the route-finding fun. The views are quite spectacular. As you drop to each successive lake, there will be waterfalls and cascades. There are also some low willows and other low-growing evergreens to avoid at times. At Ohman and Stewart Lakes, you should be able to locate a good trail which can then be followed back down to Loch Lomond, ending on the SSE corner of the reservoir. take your time on this descent. When we lived on the Front Range, this was probably our favorite hiking location. The upper lakes were seldom visited and had a nice wilderness feeling even though you were under 2 hours from the bustling metropolises. Be sure you have some kind of camera.
Links to other information, routes & trip reports for this peak that may be helpful.