Hi whiteviera

You could plug the replacement ECU straight in, but if you're not sure what caused the original unit to fail, then I'd check the wiring between the ECU and throttle body.

The wiring between the ECU and the throttle body is shown in the Crossfire Manual in section 8W-33 "Vehicle Speed Control". I think there's a copy of it on this site. There's six wires that run from pins 3,6,20,21,22 &19 on ECU plug 3 to the throttle body. If you're not sure how to check it yourself then print out that page from the manual and get an auto electrician to check it for you. It shouldn't take long to check.