As previously mentioned, the first fill is a bear. That's because you're going from zero to 2,000 ps. I recall something like 120 pumps? After that, you're going from 1,200 psi back up to 2,000. About 75 stokes will do. Not too bad to doit all in one shot. You won't want to touch one off right after that - wait a couple minutes for the heart rate to drop a bit.
I'm just shy of 50. It's no problem for me but I could see how a 3,300 psi scuba tank would be the way to go. The pump is a decent pump and should be fine to start with. The gun is great - a lot of fun. Gun runs $235 and pump is another $160 or so. You can find a used Scuba tank and filll probe for that though. The gun takes a standard foster fitting.