If you are lucky, fixing the line, pulling a vacuum and recharge is all you may need. Most of the manufacturers specify the use of dry nitrogen to purge things first, and you'd probably need to add the lubricant during the recharge process - not sure of the procedure. I'd be more worried about the compressor running overnight without refrigerant. That could have ruined it, since, when you lost the refrigerant, it probably lost a lot of the lubricating oil that circulates with it. Might have played havoc with the seals. I think a scroll compressor might fare better than a reciprocating one.
Vandalism is probably covered on your homeowners, but I think you'd have a hard time justifying a warranty repair.
It's always a good idea to do a quick visual check of things before you turn them on after sitting for awhile, although, since it is a heat pump, what were you using during the winter when heat was required? It may be that it switched to the backup resistance heating which probably cost you an arm and a leg.