Install of gitlab is pretty easy with the Omnibus install method and manual install is certainly doable. It runs ok here with 1G RAM on an Atom processor.
Everything's doable, but that is not the point. I once had a client - a one person shop kind of deal - who asked me to install a ticketing software on the same account they hosted their website from. They liked Redmine, another RoR app, so I set it up for them and suddenly everything went down, because the CPU and memory usage went above of what their plan offered. They decided it's not beneficial for them to pay for a better plan, so instead we went with a PHP based solution. So yeah, in some cases technology can be as much - if not more - important, as the list of provided features.