If he is hands on, he can do the external drive, then drag and drop the files he wants. Just makes sure it is a compatible drive. FAT 32 is a good platform.
If he is not hands on, then go to an Apple Genius bar, and they will do it all for him....free perhaps...not sure.
.doc files open with most Mac programs they are just different, and may change the setup of the document. Images etc.
Most everything is compatible, may need some downloads and etc for Windows Media player files...and windows based files.