The easiest thing to do is download and install a repack, but there is some comfort in knowing you're using the original game files. I remove the DRM on all the games I keep on my drive and most of those are from legitimate sources. I've jumped through a few hoops to manually remove DRM before.

It's not like days of old were you only needed to replace the game's exe file. You have to look at the protection on each game to see what needs to be done. I'm not familiar with that particular game so I don't know what kind of DRM it uses, but you should be able to find out with some searching.

There's no set procedure in removing DRM manually, games can vary quite a bit. Some Steam games have several layers of DRM, such as the Steam client, then 3rd party protection, then in-house protection. On the other hand, some Steam games use only the Steam client where all you need is an emulator.

Sometimes there is an easy way to manually remove DRM, sometimes there is not. You may or may not need a Steam emulator which removes the need for the Steam client to be running. Then you may or may not need a crack exe. Sometimes you can find those crack exe files stand-alone on gamecopyworld. Another place you can find stand-alone crack exe files is on cs.rin.ru. You may even need to download a whole pirate copy of a game to extract the crack exe out of it. Worst case the game uses some kind of hard DRM like Denuvo that requires multiple cracked files if the game is even cracked at all.