You could do that...but watch some PC building videos. It really isn't tough. It's like building Legos. If the Legos cost like $500, but you get the point.
And if you take it to someone you don't know, they're going to charge you out the ass. You could try to find a friend that knows about this stuff and has built one and he can kinda show you what to do. That's what I did with my first (and only PC so far) build. Took about an hour to get it together, Windows installed, and running like a normal PC once I got my parts.
After me and my friend got done, he actually mentioned how smooth this build was compared to other ones he's done. There wasn't a single problem other than my GPU driver being stupid and I just used the beta version that was up and it worked fine after that.
Building Legos is more time consuming than building computers, Especially with sets like this...
$600-700 will take you a long way (especially if we're only talking about the parts; i.e. not including peripherals, monitor(s), OS and the tower itself), but no one can really predict how slowly or quickly current parts will become obsolete.
I have very little clue as to what makes a computer. I tend to being saving money until Spring 2015 when I will start this project with about $880-$1000
go to newegg.com and go to their DIY section under computer parts. they have decently detailed tutorials explaining computer parts. go on YouTube and search for Linus Tech Tips. he has a decent tutorial on how to actually build the pc.
basically it comes down to watching and reading a bunch of tutorials enough times that you understand it. for a build, just name your budget, what parts you have, and if you need a kb/m, monitor, OS, and speakers/headphones
also 2015 is a long time to wait to start asking what parts to get now. a few generations of GPUs and CPUs will have passed by then.