Have questions about Pesco's

So I've done some research about these jewels, trying to get familiar with them. So take it easy on me huh? So I came across an overhauled pesco 280, out of a DC-3. I'm told it's been about 14 years since the rebuild, probably needing an o-ring/seal replacing by now? It's being asked for $550. THIS BEING A MAIN QUESTION OF MINE, what's everybody's 2 cents on this price?

Also, can new modern cylinders be used with aircraft pumps?