See the link below for a view of the Crosman 766
Crosman has the parts diagram online. There were 3 different versions. See the link below for the first version. http://www.crosman.com/pdf/manuals/crosman/766/C766-EVP1.pdf
There are 3 versions of the 766 see the link below for the owners manual and parts list.
See the link below it has all the Crosman Owners and Parts manuals online.
You mean "Pellets". See the link below
Crosman offers a service to locate repair shops that repair older Crosman air rifles. See the link below
Crosman offers a service to locate shops that repair air guns that are out of warranty. This service is free. See the link below. http://www.crosman.com/cs/service-center
There are three different versions of the 766 but all three load the same. All load through the oval trap door on the pistol grip. See the link below for the Owners Manual
You have two choices. 1. Go to www.crosman.com and click on "download a manual." Find a diagram for your 766 and try to repair it yourself. or. 2. Go to www.crosman.com and click on "find a service center" and locate one near you and have it repaired.
It depends on what is wrong with it, but the repairs may cost more than the rifle is worth Your talking about an air rifle that in pristine condition is only worth $60. If it was made before 1983 it's worth $90, but it has to be in like NEW condition and your needs repair. There is almost no collectors value. Personally I would take the $90 dollars and purchase a new PELLET rifle. It would be more cost effective. But that's my opinion and I collect working air guns and yes I have a working American classic model 2100 the new version of the 766 and it cost less than $60 brand new.
Go to the CROSMAN homepage and click on "find a repair center" it will help you find a repair center that handles your rifle See the related link.
You have blown seals or O-Rings. The rifle was made from 1975 to 1982. Crosman no longer makes parts for this airgun. BUT they offer a service to locate repair shops that repair the rifle. See the link Below. But first consider this. IF the rifle was in working order AND it was in perfect shape it would be worth around $50 to $60. Is it worth repairing? It would cost you almost that much to have it repaired. Today you can purchase a brand new Crosman 2100 ( almost Identical to your old 766 ) for $60 through "Pyramyd air" See the link below. It's up to you.