Can installing weight distribution hitch be a DIY project?

If you're comfortable with sockets and wrenches as well as a tape measure then I would say yes you can. One tip for when it comes time to tighten the hitch ball. Turn the hitch sideways in the receiver so the nut is pointing toward the drivers side of the tow vehicle. Now you can put your socket and bar on it and use your body weight to add some extra oomph.

Same thing goes for loosening the nut. Turn the receiver sideways so the nut points toward the passenger side and use your body weight to help break the nut free.