BB's are loaded on the left side just to the rear of the trigger. Pellets are loaded one shot at a time in the opening at the top of the rifle.
You can't it's not designed to be a repeater.
You need to state what condition it's in. without more information it is not possible to answer you.
The CROSMAN 760 Powermaster started production in 1966 then went through 8 different changes and ended in 1991
These rifles are very similar. Their are several variations of both rifles. Basically it came down to the shots that could be stored ( BB's) the original 760 only shot BB's and held 180 BB's. later versions could also shoot .177 pellets. The Pump Master had an 18 shot BB mag and a 5 shot .177 pellet mag
You will need to state the condition of the 760 if you want an estimate of value. Is it still working, Is it in poor, fair, good, very good or Excellent shape.
Pointed Pellets will have more penetration.
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
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.
It's usually just in front of the trigger guard. It should be a 9 digit number.
The Crosman 760 doesn't shoot Bullets it shoots BB's or .177 caliber Pellets.
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.
There are several versions of this model. Here is the web page for all of Crosman air guns. Owners Manuals and Schematics. See the link below.