Install it by taking the mod and dragging it into your mods folder located in Documents/BeamNG.drive/mods.
I have a fix for diff I might upload. Its still lockable using ALT + D even when the ui doesnt display the diffs properly.
yes, sounds are a known issue. this mod got pretty broken over the years with all the game updates. i am slowly working on a fix to make the hopper great again, but i can't promise anything.
I have fixed the sounds with the help from @FLyInG 2 YoUr SoUL helping @waboll on Discord. and the textures work fine for me as long as the file is unpacked. I'm surprised this still works with a couple small fixes here and there. I have some screenshots of the mod working fine here.