For starters a manual trans and an automatic aren't the same things at all, I wouldn't hesitate to change the fluid in yours at all, probably a good idea even. His auto was probably on it's way out already, did it have any problems before? I would guess that the new fluid flushed some junk out and that junk clogged something and it fried but the only way to know would be to take it apart and inspect whatever part of it died. And you might not know then. Did the dealer get it filled all the way, change the filter, and stuff like that when they changed it?

__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k