The assembly manuals are designed in a straight-forward manor. The illustrations are progressive, meaning they look the same as the robot you are building as the assembly progresses. The tools that you will need to construct the mechanics are standard shop tools, which may include, screwdrivers, pliers, a hobby knife, etc. The construction time varies depending on the kit and the person, but usually takes between three and four hours. Of course the Quadrapod or Hexapod II could take substantially longer due to the large number of components.
Some kits require the assembly of printed circuit boards.
The supplies that will be needed depends on how complex you want your robot experiment to be. In general, everything is included to build a functioning robot. The construction usually takes from between one and two hours for a simpler kit. Caution, these projects have been known to spark imaginations as well as to make one think. I have heard reports from people who purchased kits for parent child projects reporting great results.