Thanks for the tips Gary. My friend's dad runs an auto AC shop. I helped him do some work on his septic tank a few weeks back, so he REALLY owes me and said he'd be more than happy to supply me with the necessary o-rings and all the R-12 my heart desires. We're definately going to replace the dryer - my system's been open for about 3 weeks now. I'll be sure to ask him about the nitrate o-rings, but if I remember correctly, the ones I saw at his shop were green.