Good question. I have the same model and have seen the same question at other sites, but no answer, tips or tricks to getting the lower drive belt off of the crank shaft pulley with those three tabs from the frame in the way. A co-worker did offer a suggestion of removing the engine bolts to slide the engine and allow room to remove and replace the belt around the crank shaft. I don't know how hard it will be, but I will be checking it out this week to see if it is possible. If that works, the rest of the directions in the manual are pretty easy to follow.
Sam
July 2008