i just bought a 90 legacy for 75 bucks from a dealership. it has 172000 miles and runs great. the car had a impact to the rear left quarter panel and the tire took part of the impact. at speeds of 25 mph or higher i have a weird grinding whiring noise that is coming from the rear def / driveshaft area. how can i narrow it down? what can i check?

i had some buddies from work put it on the lift at work and we drained the rear def and shook the driveline. the front ujoint has some play and the rear def case had some bad wear on the input shaft. so what are my options now?