Wolf 3D is what got me interested in programming; if it wasn't for me downloading the sources and making TC's
I had the same problem with Wolfenstein 3D when I first started C. Sure they labeled the sections with little headers, but the comments just weren't there, but it probably has ore than Quake 2. It also helped that the name of the source files really didn't help much. Luckily there were online groups that gave descriptions of every file and had line numbers were certain variables were located. Plus, the assembly was commented, arent Carmack and Romero nice.