Anything more I should know, before removing my AC?

It's not compressed air in the system. It's freon. And if it's the old R12, it's quite harmful to the environment to just let it discharge. Also, it's under high pressure - so be careful. There is lubricant/oil in there with it, and it usually comes out all over everywhere with the freon. Be careful with any disconnects in the passenger compartment as the oil can get into carpets, etc.

I recommend going to an auto shop that handles a/c work, and let them evacuate the system for you. They'll pull the freon out and save it in their storage system. Once they've done that, then you can safely disassemble. Be careful where you set stuff - the oil in the filter/dryer, compressor and lines seems to leak for weeks on end.

If you go with R134 the cost isn't too bad. If you stick with R12 the cost of recharging is quite high - because the cost of R12 has skyrocketed. Ask the shop that discharges it for you how much to recharge. You'll need a new filter-dryer assembly (once you open the system, they're ruined), the freon, and the labor for pulling a vacuum and doing the charging. I'd guess $100-$150 plus the cost of the filter/drier - that assumes R134. I'd double that price for R12. That also assumes you put it all back together. Any exposed openings in the firewall or under the dash for hoses going to the evaporator coil I'd block off - duct tape or something - to be sure no debris ends up in the coil. Same for the condenser coil, hoses and compressor that you remove from the car.