Mac-1 airguns in Gardena CA. Been dealing with him for 20+ years. Old Crosmans are one of his specialties. You can get seal kits from him if you want. The 180 is usually a simple re-seal unless the exhaust valve seal is bad.
I've seen a few online tutorials on how to fix similar Crosmans, and all but two of the seals on the 180 are standard size O-rings...