I can only find install help for the steam version. If anybody knows how/ a link to how it'd be very appreciated.

The most recent information I've found is that Gentlemen of Steelport is outdated, no longer maintained, and not recommended anymore. Instead you should check out the Saint's Row Mods site:

https://www.saintsrowmods.com/forum/

If you go there you can find the up-to-date versions of all the mods included in GoS and install them individually.

From my experience this can be a little problematic at times because you might have to merge certain files manually if two mods alter the same one. I found that to be fairly uncommon though, and I managed to install almost everything I really wanted without any conflicts.

Unpack the zip to wherever you think it should stay, doubleclick the .bat which opens up a small DOS window and select which parts you want included. At that point (+ the readme) its pretty covered. But backup your save games & content of your main SR3 folder before doing anything just to be save.

As UniversalWolf said, some mods in this compilation-mod are outdated & since the creator stepped up from modder to full blown SR dev (and SR3 is kind of dated) do not expect that to change.

I myself used the GoS basic parts + the remover for that annoying tutorial popup and so far my rig has not melted.