Hello . Im Bobby
Can you give me the model number of the mower?
I cant see why they would be telling you you need a new engine because of a hyd leak.
Is it leaking Hyd oil or engine oil?
Does the engine run ok?
Ok, I understand what you got now,
Well the dealer should be able to just install a new seal on motor , As long as the shaft that seal seals against is still good. If that shaft is worn , or messed up then just installing a new seal would not work very long. It would start leaking again, But they would need to remove the old seal and inspect the shaft first,
Hope this helps, Bobby
Technician
16 years experience in small engines, Bobcat loaders, Hyd , and electrical repair.