If you bought a barreled upper, all you really need is the most basic of tools (screwdriver set, a punch or two, maybe some allen wrenches, hammer, etc), and perhaps a $20-30 castle-nut wrench. And even the latter can be circumvented with a pair of pliers.
So long as you bought a barreled upper, you're basically playing 'Legos'. But if your upper is in pieces, you've opened a whole different can of worms, some of which can require proper torquing.
BTW- If you don't have a castle nut wrench, the dealer you bought the lower from will probably help you out with that free of charge. But they're worth the $20-30 investment if you anticipate future builds.
"The Future is Unwritten"