How do i write a replacer mod for a unique weapon?

[catofriddles]

I've been watching tutorials for using the GECK to write weapon mods, but there are a few questions I can't find the answer to.

The first step is usually creating a new ID for the weapon. If I'm writing a replacer mod, do i still need to do this?

Can a weapon have more than one ability, or does a special script need to be written?

I'm hoping to add an EMP effect onto Jingwei's shocksword, with a knockdown/paralysis on a critical hit. It'd be nice if I could keep regular shock damage for non-robot/power armor targets, but I can give that up.