Depends on what you want to do with it. Keep? Sell? If you want to know what it's worth if you are thinking of selling, go to kbb.com or Edmunds.com, and use their value calculator, as Dub' said^^^. Either site will allow you to enter the options your truck has, and select a condition, which includes something to the effect of "needs TLC." It also adjusts for your region. Will give you a pretty good idea of value.
What's it worth to you? If you like the truck and want to keep it, simple PM (even with header replacement) will always be cheaper than a new or new/used truck.