2001 Chevrolet Suburban ECM b fuse

Oh, no, no, no. You do not tell the mechanic what to check. Based on your description of the symptoms and observations, they're trained to know where to start. WAY too many people get angry when they tell the mechanic to "check this" or "replace that", then it doesn't solve the problem, but they're expected to pay for the service. They did what you requested, so you can be expected to pay them. The best thing you can do is provide all the clues and details possible.

This will vary a little, but in general, most shops allow the mechanic up to one hour for an electrical diagnosis, then they tell you what they found and what it will take to fix it. In some cases, when the repair is simple, like a grounded wire, they will do the repair right away because it will take more time and more of your dollars to find you, explain what they found, and get your approval for what is needed.