Unless you have the knowledge and the tools to fix it, I don't suggest you try to make repairs yourself. I would do a search on the web for "airgun repair" and select a repair shop that can make the necessary repairs. There are shops that make a living repairing airgns. See this link
http://www.airgunarena.com/index.php/Repairs/Parts
Get the Silent Stalker, it is far superior in quality. The IGT system is much better.
The Gamo Silent Cat fires .177 caliber Pellets not BB's.
100mm.
Gamo offers instruction manuals for all their rifles. That include correct aiming with the sights. See the link below
Start with the Gamo home page "Gamousa" customer service contact. Or see the link below for shops that repair air rifles.
I own both the bonecollector is slightly higher fps but the silent cat is also a vary good airrifle just slightly less fps
Best left to a trained person.
Gamo makes some fairly good rifles and they do stand behind their products. The Whisper has the advantage of not too much of a report (Noise) when fired. In customer reviews it rates 4 1/2 stars out of 5.
Gamo makes a dozen different rifles and pistol's. I find then to be of Very Good quality. I personally prefer the Nitro piston models over Spring. The new Dynamax (PCP) looks promising but expensive.
No. it is a single cock spring system. You only need to break the barrel once to cock it and fire it.
Aurelio Gamo's birth name is Aurelio Gamo Perucha.
See this link for the owners manual. http://cdn.pyramydair.com/site/manuals/Gamo_Silent_Cat_Manual.pdf