Custom (s)npc animations

How would I go on about replacing standart hl2 skeleton walk animations with custom ones?
As of yet, I can only at all, implement custom animations to be played by a scripted NPC by setting up my very own snpc lua addon or through a choreography file + npc scene addon/console commands.
So well how would I go on about replacing the walk animations? I actually thought about simply renaming my walk animation to match the default one and expect it to be replaced, however, I haven’t tried out yet, and most importantly I viewed the standart walk anims in hlmv and noticed the ground moves and the model is still centered, somewhat unique in comparison to my animations on which the ground never moves, yet I would need that if I plan to replace the walking animation. How do I do that? Help with scripted npcs in general too? Thanks.