Jeezuz! What the heck is wrong with those people?!? What kind of fly-by-night shenanigans run a shop like that?
This is a prime example of why we should all know our own PCs and Rigs. This would be a prime time to initiate yourself into the PC building/upgrading community. Just make sure that you do some research, and never replace the case cover(s) until you have powered on the system, passed the POST (Power On Self Test) and the Operating System has loaded. Not doing so will invoke Murphy's law. Also, don't work inside the case when the power is on or the PSU is plugged in just to be on the safe side.
Jeez, at least go give those boneheads a verbal thrashing, they could have ruined your system!
[SIZE=\"1\"]E6400 @ 3.4 , Noctua 120
7900GT @ 670/1680 , VF900
2 x 1GB Patriot 6400 @ 425
WD SATA 250GB
Neo HE 550
P180 / G15 / MX1000[/SIZE]