The fact that it's empty means recovery of refrigerant is not an issue, so the good news is if you find where it's leaking you can fix it yourself if it's in a good spot. You can even install a drier yourself and leave it capped until just before taking it in for the recharge. A straight evacuation/recharge shouldn't cost more than $100 and an hour in the shop. Kinda have to guess at how much oil to add.