I have Firestone bags and installed them myself. Initially didn't have the compressor. Couple years later I installed AirLift's remote control/compressor system. I really encourage you to get the compressor right away. You can ballpark it without the compressor but I really like being able to adjust it while on the road. You really get a good feel of what is the right pressure plus sometimes conditions change and you can easily change with it this way.
You want to have the bags plumbed separately.