I had the same concerns when I did my 1.0A not long ago. Used the same video. Unless you accidentally short something you are not supposed to the risks are low but there is risk. Once you get the black bars you are set for loading the firmware.
The hardest part for me was finding something small enough to short the jumper.
I am not normally nervous when doing these things but I went forward knowing that if I mess something up I won't be able to replace the printer right away with something else. This was more of a concern than reality though.
Worst case you look for the parts you need to replace the board or the other items.
Also be aware that there is currently no way of going back to stock firmware on the 1.0A so it is a one-way trip.
I am enjoying repetier on mine.
Good Luck and let us know how it goes.
DaVinci 1.0A with Repetier .92
Simplify 3D
E3DV6