Do yourself a favor and purchase a repair manual at a parts store for the vehicle, usually about $25. Then can see if ecm is needed. They usually are pretty reliable and too costly to just replace on a guess.
The ECM should be on the driver side inner fender. It's bolted there between the fender and the battery, the best way to get at all the screws would be to remove the battery first. You should always have the battery cables disconnected before removing the connectors for the ECM anyhow. Make sure to right down the vehicles odometer reading, and have the VIN number written down aswell, not sure on this year vehicle but some of these ECM's need to be programmed after installation. Just make sure to record the odometer in case. Mind if I ask why the ECM failed?