The manual should be included with any secondhand amp purchase. Personally, I wouldn't buy one that didn't explicitly state in the add that it came with one. My rationale there is: why would I trust someone to wire an amp who can't keep track of the manual? I'll admit that's judgey and harsh, but hey, that's me... Bottlehead can sell you the manual if need be, but try to extract it from your seller first.
I'm not sure why you'd want to use the manual for testing the tubes. Testing for problems with the amp, yeah. Listening to a tube gives more real information than measuring it; you can listen and hear if a tube has died or become noisey. 12AU7s are cheap, so if it's not working, plug in another. Still not working, it's not the tube. Get a tube tester to test tubes. Get an amp to listen to music!