If you're happy with your current skimmer replace it with a similar pump. If you are not happy then upgrade. I almost went through the exact same situation today.
The pump in my reef octopus diablo died. For the price of a new pump I could almost get a new skimmer, but then I thought about it. The skimmer is working great for the tank size it's running on it just needs a new pump. Well it turned out I had some old psk 600 pumps and managed to find one that's working, but even if I didn't I would have just bought a new pump. The actual acrylic skimmer body should last almost forever. I had changed the impeller on the old pump at least twice maybe 3 times in it's life. The electronics in the pump have finally gone though.
A quality pump in an older skimmer will generally last longer then a new skimmer with an average pump.