Hi folks I own two crossmsn 760's, an older wooden stocked one and a 1979 one with the plastic stock. I taught both my son's and all my nephew's how to shoot with these so they have a lot of sentimental value. The problem is that 1979 no longer holds air. Can you recommend someone who rebuild's these? I have watched several YouTube video's but my gunsmithing skills are not up to the challenge. Thanks in advance!