W116, Specialty Tools

I can accelerate with the cruise control stalk but, it doesn't "set" (stay on?). Any troubleshooting guide available anywhere? Also, is there a cruise control "on" indicator light?

The vehicle is a 1980 300SD, 116 Chassis with nearing 300K miles. My problems began with a slight delay in the engine shutting off with the key, and has progressed to no door locks and I have to raise the hood and manually shut the engine off. I have also noticed the engine is running rough at idle, but smooths out at about 1000RPM. I intend to troubleshoot the vacuum system, but can't tell from the descriptions which of the guides I should purchase: the vacuum door lock one, the my engine doesn't shut off one, or the larger, apparently more comprehensive diesel survivor's guide.