ZXR 400 CDI box?

[Ghost]

Posted this on several other forums including 400gb but thought I'd ask here as well. I've been offered a K reg 1994 L zxr 400 that needs a bit of work, MOT, exhaust downpipes and I've been told a new cdi box. Basically wanted to ask what's involved in replacing a cdi unit, I've always thought a CDI on a bike was similar to an ECU in a car? Is this right, even on a carbed bike?
Also would it be possible to simply swap the old CDI unit for a new one, or will I need immobilisers re coding or keys and transponders or any of that lark? Finally where might I go to find a zxr 400 cdi?
Any help would be greatly appreciated thanks

[SoND]

You unplug the old one then plug in the new one.

[Ghost]