It's a great route over Am Bodach and An Garbhanach etc. For me, it's the finest walk from Kinlochleven to Fort William. I would say it's best saved for a good day. It's an unforgiving place if you make a mistake with your route. Not including Ben Nevis, the area around Steall is the biggest call out for the Lochaber Mountain Rescue and often because someone has got lost on steep ground on their descent into Glen Nevis
The route suggested by Dopeyloser is a good option also though the path shown on the map into Glen Nevis below Binnein Beag is hard to follow on the ground and goes in the wrong direction in general. It's a far easier route but not as good as the route over the tops. Another thing to consider is that the river on some occasions can be impossible to cross
All the best with your trip, it's a great area and if you are coming this far, and getting that close, the Steall Falls and upper Glen Nevis is a place not to be missed