The major assemblies come off the frame. In the video you probably saw him take the crane and cylinder assembly off the frame. The cylinder doesn't come off the crane easily, and normally should be left in place even for a through cleaning. Ditto for the trigger assembly.
If you are really interested in a detail strip of the gun and proficient at getting really small parts back together you should find the IOWEGAN Gun Guide for the GP-100. He goes into great detail on tuning the GP.
google ruger gp100 disassembly on you tube, there's an easy to follow detailed video there. Its quite easy to do and theres also a separate assembly video showing you how to put all back together..also quite easy.