I already charged it up. True it'* a "closed" system, but so are lots of other things that eventually need replenishing even without a leak. Things just work that way sometimes. Although, I agree about the leak testing, more often than not, one will exist.
Really the only problem with my AC system is that it continually cycles. It blows cold, just cycles all of the time, I dunno know why. As far as the rest goes, I have pressure gauges and have work on high pressure systems before, just not AC in particular. But hey, I've never let lack of experience stop me from doing anything before. Heck, I'd still be a 30 year old virgin if that were the case.