1995 Dodge Caravan When replacing ECM

Car died on a trip. Pulled into parking space went to check the transmission fluid, and it cut out on me. We had it towed to local garage that said the problem was the computer. Could not afford to let them fix it, so we towed it home. Finally bought a new computer (well a used one), same part number and everything plugged it in. STILL NOT WORKING! Husband has checked power going to computer, but no power going from computer to fuel pump. Did we do something wrong with the computer, it's pretty much just plugging it up, right?