At least I found it here and I bet they can answer some of the questions you just raised:
Maccari has at least two springs that he says MIGHT work in SOME Gamos.
He also has a seal or two that might fit, depending on if they've kept the same compression tube size as they had in the past. They were kind of famous for using the popular (nominal) 1"/ 25 mm compression tube for some time.
Here are two seals (read what it says there and you'll see it gives some details that may help):
I'm sorry I can't be more definite. I don't know which spring might fit one of the current Gamo rifles because I only tuned one Gamo in my life and that was 3 or 4 years ago--and that one would would have been the older 440 model, not one of the new ones. I did install a 'gold' trigger on it and it was pretty fair once I did. I did some major stoning work on another trigger for another Gamo and even that improved it to an extent--always be careful when doing trigger work--especially modifications, of course.
HTH to some extent. ("TCooper"--Todd is that you?)
Safe and Happy Shooting!
Ed Krzynowek, The Airgun Tune Meister
"We can rebuild the squirrel. Make him stronger, faster...We have the technology"---Skyler M.