Turns out that the developer tools are hidden in /Applications/Installers/Xcode Tools. I did look for /Developer, which wasn't there. And then I tried "locate .mpkg", but the locate database hadn't been built.
So now I'm running /etc/weekly manually and wondering what the best solution for that problem is, given that cron(1) doesn't really take into account that my machine isn't always on.
Still can't find X11.
The new cooling system is impressive. On the whole, my dual G5 is quieter than my PowerBook. I was joking about it sounding like the air conditioning coming on: at its loudest it's not as loud as the dual G4, and it's only ever momentarily loud.