What to do/

Bad part of a D.J.'s collection is the abuse that most of records have probably suffered. All the handling and back cueing (depending on what he played) may have hurt them.

Make a Discogs account. Add all the records with their condition. Put whole collection for sale.

Sell the whole collection to 1 buyer. You’ll be lucky to get 1$ each. Let the buyer sort them out. Most records aren’t worth much more than that wholesale. 

If you're located anywhere near the Chicago area there's a record store in Elk Grove Village called the Record Warehouse. 

A good friend and I sold the bulk of our collections there, and we were both shocked at what they offered us.

They specialize in rock and roll.

You will spend an ungodly amount of time selling them piecemeal.  That is your main consideration.