If it is stuck in the barrel, you will have to get a .177 cleaning rod to push it back out. You can purchase cleaning rods from most any large sporting goods store like Basspro or Cabelas.
Both rifles are about the same in price. The 880 is about $5 more than the 764. The 880 has a 50 round capacity. The 764 has an 18 round capacity. The 880 has a rifled barrel, the 764 has a smooth bore barrel. The 880 is rated at 750 FPS, the 764 is rated at 625 FPS. If it were me I would select the 880 over the 764
The 880 has an 11 mm dovetail mount. This BB/pellet rifle is fairly inexpensive and it works fine with a simple 4x10 scope, to put a more powerful scope would cost more than the rifle's base price. Daisy makes a 4x10 scope that works fine with this rifle
10-700 USD depending on specifics
I believe it's a Colt ( Colteer ) Semi or Bolt
See the link below for a list of places that repair airguns
It all depends on the current condition of the rifle
880
The Western Field model 880 was made by Colt. It was the Colt Colteer semi-automatic .22 LR rifle.
Half of 880= 880/2= 440
60% of 880= 60% * 880= 0.6 * 880= 528
880
45% of 880 = 45% * 880 = 0.45 * 880 = 396