What is this exactly, (I know it is an epiphone explorer, but what is it)

and how much is it worth?

I dont know exactally what it is? i guess its worth wahtever it means to you. I would just keep it.
The neck may be an epiphone neck, but the guitar is NOT an epiphone.

As for how much its worth, that all depends on the pickups/condidion/setup/woods and the list goes on.

Its oviously something that was home brewed
American Strat:
Area 61 Neck, Area 67 Middle & Bridge
Spretzel Locking Tuners
Graphtech Nut & String Tree
Lots O' Love!

JSX + Orange Cab
Fender Blues Deluxe
Deluxe Memory Man
Fulltone Full Drive 2 & OCD
H2O Chorus/Echo