If you are going to replace the bolt release yourself, put a couple layers of packing tape on your receiver to protect it from both the hammer and the punch. An errant strike with the hammer or slippage of the punch can cause a lot of heartache. Especially for putting the roll pin back in, cover the bolt release pin ears with the tape and punch a small hole in the tape where the roll pin is driven through into the ear.
When putting the roll pin drive it in very slightly so that you can just put the bolt realease in and thus index the hole in the bolt release to the roll pin. Then, you get a third hand to hold the bolt release in position while you drive the roll pin on in or to drive the roll pin while you hold the bolt release and the punch.
I would ask Bushmaster for a new roll pin also if you are going to ask them for a new bolt release.