Now if I was in your position, I would say,"HOLY S**T! MY ONLY TECH SKILL I SUCK AT!" But I once made a computer with my friend who is like a genius, but not at the same time (Sorry Steve!). From my experience if you don't want to get yelled at, accidentally break the computer/parts or smash your fingers here are some tips...

(1) Don't ask,"What do I do now?" while the person your talking to is going to need quiet to install a certain part.
(2) Don't touch shiny things that get your attention.
(3) NEVER-EVER-Say,"Relax, I know what I'm doing." to someone who really does, it only gets you laughed at.
(4) When your parents, friends or boy-friend/girl-friend ask,"So what did you do all day with your friends?" never say this if you want to impress them,"Built a super-computer! And in return it'll take over the world for me!" just kidding, here's the real thingy you shouldn't say,"Built a computer with my friends in Steve's (Or where ever you go, and if owned by someone) garage and it took all day!" I speak from personal experience.
(5) Last, but not least, just enjoy making the computer, who knows- it may become a hobby that forms into a big hobby, into a bigger hobby, and then the field of work you chose... Maybe one day a shop will open up with toutorials on how to install computer parts like Graphics Cards and all that, and maybe sell computers with the parts already in them- Orrrrrrrrrr, you can just use your computer-crafting skills to benefit only personally by making yourself a cheap yet awesome gaming computer.