Hi, I have a 97 land cruiser, was damaged in front and took out the ac dryer, I replaced it and the lines and am ready to recharge. The system was broken and open for several months and I assume its now empty and needs 134 and would like your advice for the best way to approach this situation. I am a heavy equipment mechanic so I can figure most things out, but still not a ac mechanic., and have no gauges.