Depends where its leaking. If its the rear main then its a big job!!

I have no IDEA , but: YOu look at the hours for the specific diagnosis. The shop has a labor rate. They typically try to " get the job up" by charging to change certain fluids( or what ever they can) that is included in the Remove and Replace rate for the component and this is a common practice. I charge for a can of brake cleaner even if I only use half of it.

You take the diagnosis to a Junior College that has an automotive program, find an instructor, ask him what the book rate is for the repair. He or she will show the class about estimating a job. This takes time.

Mitchell on Demand and Aldata have the rates and parts prices but these are typically more than 300 a month for a subscription.

You can also get on the phone and call several shops and give them the diagnosis and ask for an estimate, some will give you the hourly cost and total for a procedure.

My friend came over and was tripping out about his Volkswagen Diesel costing like 1600 to fix. I went to the shop and man was it nice. The bill was good, it just cost a lot. They are just high priced but not actually cheating the customer.

My boss had a bad thermostat on a car where the thermostat was right on top. Fire stone fixed it and told her it was 750. I got on the phone , she paid 500 and that was wat too much. Absolute crooks. It was two bolts, a gasket, thermostat and a top off. It must of took an hour on super slow speed. 700!!!

You do not really give any details in your question so it would be hard to give any kind of cost estimate. Good Luck