How do I turn a prop into a model for a crowbar?

I wanna make Purple Heart’s sword a remodel for the crowbar, How would I do this? And special programs needed?
I want to remodel it so it works third person, first person, and when I see someone else holding it.

:3

:zoid:

Well, what file format is the purple sword in?

Normal Gmod format. .mdl .vtf .vtx .dx80.vtf stuff like that. I have the folder all ready for someone to download.