Ouch... sounding like Frustrationsville Central.
If it is any consolation, it gets easier every time you do it.

Now to your Diff.
What do you meanby Tighten?
It is not a Friction style diff like a Bal Diff. The gears are directly drivven. If the teath on the gears are not worn and the shimming is correct it doesn't slip ever. What it does do is diff out, so the unloaded wheel gets all of the rotation.

I will try to find the Page I used as a guide (It was really good)
Will get back to you with that info ASAP