I have needed to replace several alternators over various Omegas and all due to failure of the regulator pack.
Agree with above that replacing it in situ isnt really an option unless you have hours of time/patience of a saint and the ability to get the car fully into the air so you are looking directly at the back of the alternator ,and even then unsure if its a job worth tackling from there.
Alternator really needs to be removed which isnt such a bad job and 90% done from above just the main wire retaining nut and smaller connection which are quite reachable with the 2 main locating bolts removed to allow for some wiggle room