Bill higgins

GSX250S Rider
Hi all.
Just had my 81 katana in for a dyno tune and blue slip for rego. This bike has been unregistered for over 10 years. Little issue is there is a small oil leak from the head gasket. The tune up guy suggests it could be piston rings or valve stems. I think it's just a head gasket. No blue exhaust smoke. Any advise would be appreciated.
Cheers.
Bill.