botched halfshaft replacement! need help

i tried today to replace the drivers side halfshaft. i misread the instructions and pulled the shaft out of the differential with the diff's gear stub still attached. i reinstalled the new shaft and test drove it. i realized by the 15th foot of my driveway something was wrong, my car 93 subaru legacy 2wd, made a loud mechinical pop. i checked under and sure enough the differential stub was not installed all the way. i took the shaft back out and now the car grinds while in gear and and horribly when in park, the front end is sitting off the ground on jackstands. did i kill my differential? i just bought this car 2 weeks ago, any advice, repair options is much appreciated!!