Is it easy to replace the engine bay fuse box?

Hi
I have an 04 megane with a busted fuse box in the engine bay. She does not go and the dealers advice was to scrap the car because it would cost to much money to get a new box and related wiring harness to do the fix. I was looking at my manual and it said that when replacing the fuse box you should tell the computer. My question is is this really necessary? I can do the job of replacing the box and harness myself with second hand parts, but the last thing I want to do is take it back to the dealer on the back of a truck.

Cheers