Replace Finder with Forklift
Discussion here on replacing Finder with nautilus.

You can add a Quit menu item to Finder and quit it like so:

defaults write com.apple.Finder QuitMenuItem 1; killall Finder


Now, run ForkLift.

You could try (WARNING: DANGEROUS) to rename ForkLift2.app as Finder.app and replace Finder.app, but I think this would probably just cause problems, possibly severe ones.

What do you mean by "open folders, paths, etc."? Almost all Finder interactions on my computer are initiated by me. Just use ForkLift instead. The only time something else uses Finder is if I double-click on a DMG, then it opens in Finder. If you have this, or other specific use cases that you would like to have interact with ForkLift, please clarify or post additional specific questions.