How to Pak Uassets

I have unpaked episode 1-3 of LIS2 (What I wanted to mod) All I want to do is switch character models. It’s in uasset form and I don’t know what I’m doing at all at this point. I have my models I wanted to switch with. I just can’t understand how to do this. I’m not an expert at unreal. I just wanted to mod a game and now I’m stuck of what to do.

Update

Okay I messed around a bit more and I was able to import my model in unreal. So, I suppose my next question would be what I do next.

I have files like these to replace with my model.
head_hair.uex.p
head_hair.uasset
CH_SF_FRND.uex.p
CH_SF_FRND.uasset

What do I do? How to make the files into this? Then when I do what about paks when I need reseal the files?