The aircon gas also contains some special oil, that circulates when the system is running. This oil lubricates the pump, but importantly, also keeps the seals, in the pump and at each pipe joint, supple. Without the oil, the seals shrink, allowing the gas out.Re the aircon would you service it now or wait for spring?
The longer it is left without gas, the more likely it is that the seals will fail. Whilst seals are cheap, the labour is not, as they are fiddly to fit. A new pump is around £200, or more, plus fitting.
Of course, you have no idea how long it has been out of action. Most garages now service aircon. They can evacuate the system, and apply a vacuum, and see if it holds. If it won't hold, there is an obvious leak. At that point, you can just leave it, never to work again, and cook in the little greenhouse in the summer, or the next stage is to pressurise it with nitrogen and search for the leak. Once found, a quote for repair will be forthcoming. Of course, after any such leak is fixed, it could still need a pump.