How would i go about modding and using steamworks

So I’ve been struggling with this for more than 3 weeks trying to collect up the information I need to really work with this but I just keep walking into “roadblocks”.
My first question would be do i need to pack the files in the actual Original Game if I would only want to do simple mods which only would include Custom materials and Sounds or can i make pretty much an empty project with a few assets(Mainly for people to test) which I could share around to people interested in modding the project but keeping my file safe.

Second of all how would I go about loading that information out of a pak file for example when it was downloaded via steam workshop it will end up on a different path from the engine itself? How will I be able to use that path to load materials or music out of the file?

And third is will I have to distribute Steam CMD or are their other possibilities.

I hope i worded myself properly with this issue,
And thanks anyone that will reply in advance ^^