What radios does it have? How's the paint? The interior? If all are average, a 172 with a runout engine (I know it may be running great and could go another 1000 hours) is probably not a great deal at 25K. It's not terrible but it's not great.
Unless you needed the additional carrying capacity, I would imagine the 172 would be a lot less fun to fly than your current ride. When I fly a 172 it feels like driving a loaded dump truck compared to the towplane (180hp A150L).
Just an opinion and your eyes on the plane in question trumps any opinion I have sight unseen. I'm sure you'll weigh all the options and your intended mission before making a decision.
