That rifle was that price probably because it is being discontinued. However, all that means is you got it for a very good price.
There are a few ways to fill the rifle. I will list them in order of initial expense starting with the least expensive and work on to the most expensive. With any of them, you will need to make sure you have the proper fill adapter for your particular rifle.
First, is by using a hand pump (they look like a bicycle pump but are actually multi stage compressors). The one I recommend if you want to go this route is the Hill. The Hill pump seems to hold up better and does not have to be rebuilt nearly as often as the Benjamin, AirForce, or even the FX.
The second way, is to fill with a SCUBA tank. You can get these filled at any dive shop. The problem with SCUBA tanks is that you can only get them filled to about 3000 psi or so. If you fill your rifle all the way up to its rated 2900 psi, you don't get many fills out of the tank before the pressure becomes too low.
The third way, is to fill with a SCBA tank. These carbon fiber tanks hold 4500 psi and will fill your rifle several times before you have to get the tank refilled. The problem with these tanks is not all dive shops can fill to the full 4500 psi pressure. If you are fortunate to live and play close to a shop that can fill them, then this is often the best route, unless you want and like a bit of exercise.
The fourth way is to lease a 6000 psi nitrogen bottle from a welding supply house. You will get enough fills out of such a tank that you may not need to have it filled within a couple of years. You will need a high pressure regulator for this as the high pressure of this tank will exceed the safety factor of your rifle.
The final way is to buy a compressor that either plugs into the wall, or runs on a gasoline motor to fill your rifle directly. The common brands are the Shoe Box, Omega, and Daystate. There are others as well.
Now, for sighting in. This rifle of yours is not just a 20 yard gun. It is quite capable of good accuracy and power for many small game critters and pests out to 50 yards or more. It probably won't win National, or International benchrest competitions, but it is likely to surprise you when you feed it the right pellets.
What I do for a sight in distance with my .177 is 30 meters (33 yards). This gives me a "don't worry about trajectory" zone from 15 to 40 yards. The .22 in the power you have will be not all that much different, but you might extend that out to a 35 meter zero for optimum trajectory. There is a free air gun ballistics program that you can download from Hawke Sport Optics called Chairgun. You can play with this to find out what sight in distance best suits your shooting and set-up. Scope height makes quite a bit of difference as does actual pellet and velocity.
All in all, welcome to the wonderful world of PCP (pre charged pneumatic) airgunning.