My 94 LaSabre will not always turn over. Cranks, but do not always get. A spark (I used a spark plug tester) Sometimes will die while driving but will start up and then run rough, with the service engine soon light.
One mechanic thinks it's the distributer, another said I don't have distributer, and it's the coils, a neighbor thinks it's the brain that connects to the ignition. Please help! Too many cooks in the kitchen! Thank you.

Did the mechanic check for and find any codes?

Your LaSabre doesn't have a distributor. I would plug your existing coils into a new Ignition Control Module (ICM). They are problematic components and I recommend replacing them every 120,000 miles or 10 years, whichever comes first. You should easily be able to do it yourself. This will likely solve the problem.