I just purchased a 1980 25 ft Oday, and the only thing I can find wrong with it is the rocker pumps on the sinks do not work! I am not new to boating, but first sailboat and I can't find replacements at local West Marine (Charleston SC).
Find out the make of the pump. I have a Fynspray WS61 chrome galley pump that came with my 1986 O'Day 222 and I've rebuilt it a few times since I've owned my boat.
My youngest son lives close to the industrial park in New Bedford Ma. where Imtra is located and I was able to have him drive down there and buy a kit from them at their warehouse. If your Galley pump was manufactured by Fynspray, you should be able to buy a service kit for your rocker pump for about $12 at Imtra.
http://www.imtra.com/other-products-fynspray-pumps.htm
Usually, the rubber washer in these pumps will dry out and you can get them serviceable again with a little vegetable oil. Just apply a little Wesson oil to any rubber washers and moving parts with a paper towel and see if that doesn't cure it.
While it's true that there are probably better galley pumps out there on the market, eventually they too will need maintenance.
Check out the prices of these pumps. I'm wondering how much a good pump sells for. Myself, I'd opt for the kit.
Joe