If it was easy everyone would do it......

Bought a 72 340 Duster about 6 months ago......I am no mechanic and have taken on a huge project.....The latest issue I have run into is the original matching number engine which runs pretty good and came in the car has an exhaust leak on the passenger side. Further inspection of the problem today and I found a broken stud closest to the firewall. I don't know if it can be drilled out and fixed with the head on the engine. Has anyone done the work needed without removing the head?