Yes, you can use HPA. The bottles usually output at a regulated 850psi which is the same as CO2 so they are a direct replacement. Just make sure you get a high (850psi) output tank and not a low (450psi) output tank.
You won't be able to fill your own tanks. Most home compressors only output up to about 125 - 150 psi. You need to be able to fill your bottles to 3000 or 4500 psi which can only be done with heavy duty industrial compressors that are very expensive. If you want to keep your own air around you can have a reserve by using a scuba tank and a scuba fill station. You will be able to get several near fills with a scuba tank and they only cost between $5 - $10 to get filled at a dive shop.
Crossfire is a good brand of HPA regulator. I have a couple of Pure Energy regulator. They aren't as good as the Crossfire, but I haven't had any issues with them keeping up to any of my guns. Any bottle will do as long as its carbon fibre which makes it light and tough.
When you clean the gun, make sure the oil you use is non-petroleum based synthetic oil so it won't eat the orings. I use a good light synthetic airtool oil and haven't had problems in years.
You might want to consider upgrading your valve to level 10 which a bolt upgrade. It will prevent chops, so you won't have to worry about cleaning out your barrel near as often. If you do this upgrade you will most likely also have to upgrade your regulator piston assembly because your original one is set to a lower safety release pressure than level 10 guns operate at.
Except for the Automag in front, its usually the man behind the equipment that counts.