Ok, here's a "benchmark" test I did just to find out...
In System Info I had the following KB used:
17,400 - before backup
17,428 - after backup
17,408 - after reboot
18,828 - after installing tkc explorer demo
18,840 - after reboot
17,396 - after restore (no reset)
17,336 - after reboot
So it appears restore alone wipes out the internal flash prior to restoring.
As for the tkc explorer "demo", I had purchased it for the 5500, but it won't work on the 1000, and I'm not about to purchase it again when Tree!Explorer+ is so great.
But I thought it was a nice sized program to install for testing.