If you have to remove the top cover, try to leave the accelerator lever (with the coil springs) in place. The accelerator lever is mounted to a splined shaft, and its orientation relative to the splines changes how the accelerator pedal works. If you must remove the lever, mark it and the splined shaft so you can reassemble it correctly.
Nothing too bad will happen if you get it wrong, you'll just find that the engine will idle too fast or too slow (depending on which way out it is), and the engine might be suuuper sluggish. In that case remove the lever and reposition it until everything's back to normal.
There's a full rebuild thread, with pictures, here:
http://www.brick-yard.co.uk/forum/ve-injector-pump-rebuild-in-colour_topic17456.html
Best to read it in reverse order, and pay attention to the bits where they say "of course we measured this before disassembly". Replacing seals doesn't require quite this level of teardown, but it's good to know which bolts and adjusters you should avoid.