Engine Module on 1991 Buick Skylark

How would I find and replace the engine/ignition module?

Asked by for the 1991 Buick Skylark
Finding and replacing the module is no problem diagnosing and testing the module to prove it is faulty is the problem. The module is at the base of the two ignition coil packs on the engine.
How do you replace the IEM when the 4 bolts our loose in the backing plate? Do you take the backing plate off and then install thr IEM, then reinstall the plate?