I just got the replacement dampener back today in the mail.
So all good on the company's part.
In regards to doing up the big bolt, on the RB26, putting it in gear isn't enough unless the car won't move when you put a 2 metre long pole on the end of your breaker bar!
My way was to drill a hole in line with the flywheel teeth in the bellhousing to fit a big flat blade screw driver in there to lock the flywheel.
Had a mate do up the bolt bit by bit with an extension pole while I was underneath holding the screwdriver.
Worked very well.
Otherwise I use a flywheel lock made by Eric when the gbox is off the engine.