You mention the dealership. Please tell us it's not a Ford dealership. There are diesel shops everywhere that know more and charge less. The valve cover gaskets liked to leak and can make it look a lot worse than it really is. They are a little pricey as they have wiring harnesses built in but not $2500 worth
The 7.3s were basically indestructible and at your mileage fixing it is the way to go. If it had that many leaks you would have noticed it by now even if you only smelled them.
Good luck with it but read posts about the 6.0s before buying one. Without receipts they are not bulletproofed. Heck, now people selling DAs and Cummins are saying they are bulletproofed.