Is it hard to change ecu and key code box in my 1.4 1996 honda civic , and it has an immobilizer what's really the best way to start my car immedietly

Because of the immobilizer, I would get your current ECM remanufactured. There are outfits that specialize in it. As far as removing and replacing the ECM, it's not hard at all. Here's what's involved:

Engine Control Module (ECM) Replacement

1. Disconnect negative battery cable, after recording radio codes.

2. Remove right door sill molding, pull carpet back, and expose ECM.

3. Remove three 10mm bolts and one 10mm nut securing ECM cover.

4. Separate ECM cover from harness carefully.

5. Press connector release, going to connectors A, B, and D, and carefully pry connectors from ECM, using a small screwdriver.

6. Spray connectors with WD-40, plug connectors into new ECM, and button things up.

I know a company that can assist with your ecu repair. :cool:
They provide technical support along with the repair.
Fast shipping and a warranty, too!

The ecu to your honda should be on the floorboard in the passengers feet area if you pull the rug back you will see it bolted to the floor remove the four nuts the hold it down and remove the three connectors connected to the ecu and its free to remove