Flat rate time is approx 1.8 for the regulator, so figure half a day for someone who doesn't do it often to be safe. Its not that big a pain and yes you do have to drill out rivets on most of them unless they have already been replaced once , in which case they are bolted in with M6x10 bolts and nuts ,
Not in the case of most of them i've worked on . Here is a photo of the gear tooth failure, not a plastic washer