They're awesome saws and have a unique sound, much different than the saws of today. Parts are widely available for them, check ebay, chainsawr.com, and even Bailey's may have some (I think they tend to newer saws though). Awesome firewood saw and easy to work on. Please whatever you do do not sell it and buy one of the new craftsman or homelite products thinking its the same, treasure the piece of machinery you have inherited. My XL 12 was the first saw I ever got, got her free from a lady selling things she inherited from her dad shortly after his death. It was very sentimental to her, she said it was her Dad's favorite saw and had a tear in her eye when handing it over to me.
In terms of fixing, they generally really only need fuel line, fuel filter, and a carb kit. Just pull out the old line and replace it with the same size weedeater fuel line instead of hunting down an nos version. Best of luck