Sounds like a decent buy, but the blades were most likely 16, 18 or 20" blades, originally. If you want to know, measure from the axle to the closest part on the frame. Leave about 1" off of the measurement for clearance and double the number to find the maximum blade diameter that the disc originally had.
Nevertheless, if it still tills decently, then use it as it is. Blades can be purchased from many tractor dealers and aftermarket are usually the best way to go, but especially with an older disc like yours.
For parts, go to any New Holland dealer or go online to Messicks Equipment, look under parts, put in Dearborn Disc and select which model you have. Some parts are obsolete, but can be had aftermarket.
What parts do you need and is yours a tandem or offset?
Have fun and keep farming! America needs you.