A script for changing model?

Can someone provide me a script for this (if it’s possible):
When NPC(specific one) is hurt for like 50% it changes it’s model, but keeps it’s weapons. Talking for rebel right now.

And also, please tell me where to put it,

Thanks in advance!
Warlord422

(wrong post icon sorry)

bump

I’m truly not trying to be mean, but why would you want something to switch models once it’s 50% dead? You want a combine soldier to suddenly turn into a pigeon with an ak47 or something? No offense, I swear im not trying to be mean I am just trying to understand.