Dont you just love it when they dont write down any of the error messages? I always do...
The only way to be sure is to check the components you mentioned on a different MB...I would add them one at a time...run for a little while (if running at all ) before adding next one..
If none of them have a problem...then it's probably with the MB...
You could also reverse this test by using your known-to-be-working components on the MB...if it works...then the problem is with one of their components
One other thing, though..although very doubtful..is there any way the board could be shorting out?
You said the psu blew...any tiny metal particles? (Look for a black-ish dust.)
This, ofcourse, would depend on if the psu REALLY blew, or if it just went "out." (Ive only seen one psu do an actual "blow.")
You might want to ask them if anyone did any tightening of the MB screws...
Also, how long after they installed the psu did everything work fine?
Were the error messages displaying while booting, or after OS loaded?