Your description of the hike is exactly what I meant.
A rather long hike, yes, but one that let you see a great variety of landscape (and wildlife according to my experience).
It is true that the start and end TH are not the same, however there are shuttle services available to connect the 2 trailheads during summer time in the park.
The easiest way to go is to park at the St Mary visitor center (east side) and take the private 10$/person shuttle to go to the Many Glacier trailhead in the morning (East side shuttle, only a few shuttles per day:
http://www.glacierparkinc.com/images/_userfiles/files/Shuttle%20Brochure_lowres.pdf).
At the end of the hike at Logan Pass, you will be able to use the free shuttle service of the park to go back to your car (several shuttles per hour :
http://www.nps.gov/glac/planyourvisit/shuttles.htm).
I hope it might help, Glacier is a really beautiful park.
