Making jump to replace motor should involve more than one opinion usually. If you are very lucky, just heater core and parts. If sorta lucky, just head gaskets. If dismal, cracked block.

As to value, KBB.com; or www.statewidelist.com, to see what they are going for in your area.

This is a time of year that service manager's wives all go shopping....

 

Only $6500 for a new engine? Thats cheap!!
The truck is only worth what you are willing to put into it.
You just bought it, do you still owe? Or did you pay cash?
Do you want to make payments on a car you cant drive?
If you still owe you will be upside down, no way you can sell it for what its worth let alone what you owe with a blown engine.

 

In it's current condition it is worth very little. From what you have said so far, it seems like you would not be able to do much yourself either. You are facing a very expensive road ahead with this vehicle. Even after repair, I doubt you could sell it for the repair cost alone.

How much did you pay for it a month ago? It may have looked nice then and if you paid what most people will claim is retail value, do not expect to be able to resll it for that price after repair. If you really plan to keep it, it will take years of driving to recoup what the total is going to be having someone put either a new or used engine in it.

Sorry to be blunt, but I do think that is what you are up against.