This could really turn out to be a large but very interesting project! Don't just take them into any record shop that deals in resale unless you already know what among them is valuable. They could very well lowball you worse than a GC trade in!
I've had that happen before (with specialty magazines that are long out of print from the late 60s - early 80s)... Dude nearly jumped out of his seat while trying to keep a poker face and offered me $50 per box. I sold him 2 boxes (of 60-80ea) because I didn't know any better. Some eBay research showed them selling for between $10-50ea on average, with some closer to 100! Luckily, I had about a dozen boxes of them, and the remainder actually funded my cross country move.
You should be able to tell right off the bat which are mass produced and near worthless, which will likely be the biggest percentage of them. First pressings in great condition of anything pre the early-mid 80s (when records got flimsy) could be worth something, even 80s stuff that had an extremely limited run in a very specific genre could be worth researching further. Colored vinyl and import pressings could fetch more than usual. Seriously, go into a good resale shop and see what those old Zappa and early VU albums are selling for... I think you'll be surprised!
Make 3 piles... 1) keepers 2) maybe, and 3) donation, or sell as a lot to a record store that resells mostly inexpensive vinyl.
DISCOGS and eBay's ended auctions are your friend. I think DISCOGS even has a template to help you catalog your collection easier, and I'm positive they have listed almost every pressing of almost every album that makes it easier to find out exactly what you have in your hand.
Personally, I'd love to see the finished list out of curiosity. Good luck
