Depends on what's causing the leak. Your pic seems to elude to the compressor casting having a hole in it. If that is the case then you need a new compressor. If it is leaking out of the pulley shaft, then you need a new compressor too.
Cross your fingers that a hose is loose, maybe it just needs tightened down. In which case, it is a total DIY.
If it is a compressor, then that depends on your mechanical ability.
I think I would probably attempt a compressor change. Mine sounds like it is compressing marbles, but it has lasted 2 summers so far and still puts out cold air. I am looking at prices and methods to do it for the eventual day when she kicks though.
A shop is mandated by law (even with R134a) to evacuate the system and recover the freon. Because R134a is supposed to be safe, they do sell vacuum pumps and re-charge kits at bavauto and any other finer auto part store.
If you replace the compressor, you will need this vacuum pump to clear the system of air. If it is just a hose loose (assuming you don't need a new hose), then a recharge kit should do you. Get one with a pressure guage. It helps.
Hope this helps. A/C work is rough because you need special tools and pumps and need to understand operating pressures and stuff. Most of that info is available on the web as are the tools, so its up to you.
If you have more money than brains, take it to a shop. If not, give a DIY a whirl. The worst that could happen is you not have A/C for the winter.
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