I notice my ac was not cooling as well as it usualyl does so I decided to add some 134 to it. after doing so, I could hear a hissing sound and see bubbling coming out of the top of the ac compressor. This leads me to believe the o rings are bad. Can anyone give some advice on changing these? Will I have to put a vacuum on it afterward?

Is there something else like a gasket on top as well.