Rather than replacment, you may want to consider a rebuild when the time comes (seems 5000 hours is just getting broken in ;-)
You can largely do it yourself at a fraction of the cost of new. I did mine at about the same hours as yours back in '04 (due to probs other than hours.) Sent the injectors & injector pump to a shop for about $700 (that's not DIY territory!), paid $2100 for a complete rebuild kit from Perkins, paid $300 to a local mechanic for a few hours of his time & coaching when needed (and he had a couple of tools I didn't). Lifted the engine up with the halyards and set it back down in the cockpit to work on it. Finished in about a week and the best part is you really know your engine when you're done.
If you're not into DIY that much, you can have a shop rebuild it for you, again, much more economically than a new engine. Plus you know it'll fit back in and the connections/controls/gauges don't need modifying.
Craig & Katherine, s/v SANGARIS, Santorin #68