My first PC was also my first build... maybe I just got lucky, but the assembly and initial setup went very well. I have a lot of A/V tech and general mechanical experience, but I was in very unfamiliar waters with this project. If I can do it, so can you.
If you still decide to buy a "turnkey" system, whatever you do, don't just walk into a retail place and expect the sales staff to hook you up with exactly what you want... better to order a rig from some place that will customize for you.
I can't recommend any particular hardware, but here's some pointers for what it's worth:
-Don't get hung up on "future-proofing". Just get what you need now, and expect to upgrade. It's inevitable.
-The trickiest part of selecting components by ordering from NewEgg or whoever is determining compatibility. Most distributors don't offer that kind of support; expect to do a lot of research... as you can see, there are some savvy builders right here; they can assess your "wish list" for you.
-If your CPU heatsink comes with thermal paste on it already and you want to use your own, be sure to remove the factory paste
first...

I... uh... know some moron who made that mistake; what an idiot!
