Not a bad looking rig. The way I would approach it is, I typically give the rig a 250k lifetime on the drivetrain, I realize they can go longer, but that's usually the ballpark number I've experienced...you may be willing to go longer. But for sake of argument, say you can expect 250k out of that thing. If it already has 200k, how long will it take you to eat up the remaining 50k. Then figure in how much an engine rebuild and/or tranny rebuild will cost you over the life of ownership (I exclude the 'little' things because those aren't big ticket items and are typically lumped in to cost of ownership for me). Now factor in those costs to the 3k...see what number that puts you at, then see what else that could buy you.
Maybe you decide you'll keep that vehicle forever and an engine/tranny rebuild is cheaper than purchase of another vehicle. Maybe you'll decide you can milk that last 50k for 10 years and then you'll just throw the vehicle away. Or maybe you'll decide that last 50k will only last you 2 years and it's not worth it. Or maybe you'll be somewhere in between.