Should I buy a Case skid steer loader 1979 with 10000 hours?

Yes, depending on price. Most bargain priced Case skid steers are for sale by owners that do not know what, if anything, is wrong with the machine. Therefore you have an uneducated seller trying to trip off a high hour machine. Parts and service is available for most Case machines. You might be buying yourself a project, but, if the price is right>>>>>