Assuming you either paid, or used miles for your first class ticket, you will have lounge access (upgrades are not included for lounge access).

I was under the impression the mileage cut-off is 2,100 flight miles, but looking at the AS Policy now, it appears they reduced it to 2,000 (or I had it wrong).

Hopefully you are departing from the N Gates so you can use the Flagship Alaska Lounge, as it is a great lounge. With that said, you can still use it regardless of which gate you are departing from.

Edit: if you are checking bags, you won't be able to drop them off more than 4 hours before your flight, so 11:50AM is the earliest you can drop them off and go through security.