1998 Chevrolet Blazer Grounding Wires Missing

A rebuilt engine was installed almost 2 years ago and the truck has been driven about 60,000 miles since then. The repair shop I take it to told me that some of the grounding wires were not connected when the rebuilt engine was installed - but they wanted to charge me almost $200 to fix them and since it had been driven for a year in that condition, I really didn't think anything of it. That is until recently when my dashboard & headlights have begun to flicker. It might happen when I've first started the engine or when I'm driving. It's happened at 40mph and 70mph. While the lights are flickering the amp meter will bounce a little but it never goes below 14. The battery was replaced 2 weeks ago. Convinced that we had a failing voltage meter in the alternator, I stopped at the local shop to buy one. The guys there strongly suggested that I check out the grounding wires first and that it was a job that could be done at home.

So here's the question: Where are the grounding wires supposed to be? How many should there be? I haven't bought the repair manual for this vehicle... Yet :)

Thanks for the help!