To remove solder
1. Preheat soldering iron like you normaly would
2. Get something to wick away melted solder ( paper, sponge ect)
3. Melt the solder with soldering iron and wick it away.
I will second Joeblo (I am a real builder) on properly building a motor mount instead of electical tape. A simple block of wood with a hole the same diameter would work fine as a better mount. Now that I think about it if you have a couple of spare boards you could figure it out with trial error and a multimeter.
Pictures of both sides of the circuit board would be more helpfull than that video.
Good luck figuring it out