Hello & welcome, sorry to hear about your problems,
Boxer just refers to the engine layout it's pistons are horizontally opposed (lie flat opposite each other) where as in a standard car they are standing up in the engine bay when you look at the car,
If it's snapped then the only option is to pull the engine out and take the heads off as the valves will have more than likely dropped and interfered with the pistons, a complete refurb would be need to make sure there's no nasty bits of metal stuck somewhere they shouldn't be.
A replacement engine may be cheaper depends on what you wnat to spend and how much the car is worth