The weapon’s properties and mesh are under “weapgun” in the content browser, if you’re doing a third person game you don’t need to worry about the “hands” because that’s the first person mesh (only you see it in a multiplayer game) which means you can simply replace it with the third person mesh (what other people see, your full body) and it will look okay (but probably give you motion sickness if you aim up or down, fair warning).
Rather than looking for specific tutorials I’d recommend you learn some fundamentals through Epic’s tutorials as they’re quite good, and from there look for more general videos, metal game studios has a few decent ones if you look them up on YouTube.