Does it have 2 burst discs, a 1800psi and a higher one. If it doesn't have a 1800psi burst disc there will be a vent hole to release pressure if the reg fails.
Well obviously you need to find out exactly where the leak is coming from otherwise you'll just end up taking bits off that don't need to be taken off, personally i use leak detector spray to spray onto the area i think the air is coming from. Only when you've found out exactly where it's coming from can we advise you on how to fix it.