Crosman has some parts available online. See the link below for all the Crosman rifle parts manuals and owners manuals. You can order parts from Crosman.
The CROSMAN 760 Powermaster started production in 1966 then went through 8 different changes and ended in 1991
You need to state what condition it's in. without more information it is not possible to answer you.
It all depends on the current condition of the rifle. You have not given description so it is not possible to give an estimate of value
The Remington Airmaster is rated at 725 FPS (Feet Per Second). The Crosman 760 Powermaster is rated at 595 FPS and the 760P is rated at 600 FPS. 10 pumps each.
It's usually just in front of the trigger guard. It should be a 9 digit number.
You have two choices. First: Crosman has the parts manuals online along with the owners manuals. (See the links below) there are several versions of the 760 so look at each one to find yours. Then contact Crosman for the parts you need if they are available. (Customer contact.) Second: If you have no luck with that, Crosman offers a free service to locate shops that repair old Crosman products. So see the 3 links below.
There are 4 different versions of the 66 Powermaster by Crosman. See the link below for all the Crosman rifle models, parts list and owners manuals https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=powermaster
The Crosman 760 doesn't shoot Bullets it shoots BB's or .177 caliber Pellets.
There are several versions of the 760. See the link below for all of the crosman models with dates and manuals.
Crosman has made 5 or 6 versions of the 760 and has parts available (See the link below for the older 760 parts list. ) I would contact Crosman Customer service to order the parts (see the Link below)
Crosman 66 Powermaster: 100%=$80, 95%=$65, 90%=$45, 80%=$35, 60%=$20 (50%= no value) Blue book of Airguns