How much should I pay for this truck?

no fixing the odometer just means getting one that works. I suggest you go to carcomplaints.com and see what there is about this vehicle and go to nada guide to see what kind of price Im thinking that with an unknown mileage there is no way to prove what it really is. Other than looking at the drivers seat where someone is always sitting. At 100,000 it should be in decent shape, if its pretty tore up the mileage is a lot higher than represented.