It might be helpful to take a look at this:
http://www.sglocks.com/pdf/book_mech_locks.pdf
On page 6, there's a procedure for lining up the wheels to change the combination. You'll want to do something like this. You need to get all three wheels lines up so that the notches in each wheel are directly under the hook on the lever. This will let the lever drop and you can turn the wheel to retract the bolt. If you can see the wheels moving, then you should be able to see the notches and get them in line. The pdf linked there explains some of how these locks work, and you might also take a look at the howstuffworks.com entry on safecracking.
As long as you're looking inside, look for someplace you could pry with a long screwdriver to pull back the bolts that hold on the door. Then you can figure out the combination working in a more comfortable position.
It's lucky for you that hole is there (and the cover's off the lock). I wonder if someone else had similar difficulties? Since you can see what's going on inside the lock, you're 90% of the way there.