1998 Chevy Express Acceleration

I have a 1998 chevy express 15 passenger van, v8, automatic trans. Twice now we have been on the highway at 55-60 mph and without warning, the engine begins to die out when trying to accelerate. We end up in the emergency lane going idle speed the rest of the way home. It is not a consistent problem. The repair shop could not find a problem or get it to act up. Changed the fuel filter. A few days later, same problem. Otherwise, the van has been running like a top. Repair shop says next step is the catalytic converters. Big cost. Friend says it is probably the Electronic control module, a common problem on the 98 3500. He says I can replace it myself. What do you think?