Physically programming the arduino is fairly straight forward and is done via a serial port. But writing the code is beyond my expertise. All of the code I wrote for my progressive project and other stuff was done with Basic Micro which is very similar to the Basic Stamp. When I modded my quadracopter, I basically just used the program someone else supplied. The code was quite a bit different from what I was used to, so I never bothered to try and learn it.
If he more or less has a "kit", then it may be pretty simple. Not really much to the mechanical stuff. Basically four motors that are controlled with the processor board. That board may already have everything on it (i.e. the gyro, etc) or there may be separate boards. I know most of the arduino stuff is "standardized" to where you just stack boards on top of each other and they talk to each other through the common mating connector. If it did not come with the programing software, that is a free download from the arduino site.