Here is a YouTube link that will give you a good step by step to follow when doing a reseal to your Avenge-X. The video is not in English but you can just turn off the volume and pay attention to the process:
I just did a reseal to my X following the video above. It went without any issues except the O-rings I was replacing had failed by becoming hard and frozen in place. I suggest you go as far as you are comfortable to replace the original seals and then maybe shop for aftermarket O-rings from Internet vendors because the factory O-rings are not all that.