Thank you so much for the advice. I had no idea it was so easy to become certified, and I didn't know that the stuff was even sold in this state. To make a long story short, I became certified this afternoon and bought 1 1/2 lbs of R12 at a total cost of $60. I charged the system and it blows frigid air. I forgot just how nice that A/C system is when it is working. Looks like I will be able to tolerate the rest of the summer.
Thanks a million,
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K