Lee, congrats on your new purchase, you're going to love it
I recently bought a 100 and have been blown away by the quality of the images I've got from it so far.
Just be prepared...the 120 is quite a big scope...the friendly Tasco/Skywatcher chap at AstroFest had one on display. Substantially larger than the 100, and they come in well padded travel cases.
The flattener is just a flattener not a reducer.