That seems pretty high for the condition of the engine, and the condition of the airplane, which matter a lot more than the avionics. I bought my plane for not too much more than that, and it's in fantastic shape mechanically, and is pretty decently equipped.
I'd recommend walking away. Take the $16k, add a few to it and go get yourself a decent plane. The $10k you'd spend working on the engine in this one could easily get you a 430W installed.
