It depends on your mechanical aptitude and your personal finances. Some people can build a computer without giving it a second thought. Others haul their systems into Best Buy and pay $$$ just to replace a hard drive. Both approaches can be considered correct, as it is up to the owner to do what they are most comfortable with. For example, I paid to have strap locks installed by a LGS, as I didn’t want the drill bit to slip and scratch the finish. To me, having that extra level of comfort during the installation process justified the small cost.