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The red o-ring is on the orifice which you will want to carefully remove for cleaning. It is a -902 which is just a hair thinner than a -010. The -010 may work as a replacement but may be too tight. After unscrewing the orifice, you will need to push it out with something that will not damage the knife edge. I use a long rubber erasure. Handle it very carefully as one oops will cost $10 to $25 depending on plastic or metal.
Sounds like the first 109 has the modern duro poppet which takes the replaceable seat. You shou8ld ba able to lift it out with a fingernail (or straight pick from the side if the fingernail fails). The seat can be flipped if the other side has not already been used. Some tech may have applied a little glue that will make it harder to remove. Glue is unnecessary. The seat will stay in place without it. The "crap" is most likely a more than generous application of silicon grease.
The second one sounds like the older poppet but I have never been able to seperate the poppet from the seat. The seat is attached to the end of the poppet. As a temporary measure, I have sanded the groove out of those seats just to make sure everything was working while I went shopping for a Duro poppet. The "green oxidation" (verdigris) is fairly easily removed with a light acid (50/50 vinegar and hot water) bath. 5 to 10 minutes or 2 to 3 minutes in an ultrasonic cleaner. Wash in detergent first to remove all grease and oils. After the bath, rinse in a neutralizing solutio (baking powder and water), then rinse in hot water, dry, and inspect. If you still see green that you want to remove, repeat. But don't overdue it as it will also remove chrome and reveal the copper or brass underlayer. Scubapro stopped using colored o-rings around 2000 so the black o-ring on the adjuster suggests aftermarket o-rings or a leak repair without updating the poppet.
For lubricant, you should use Tribolube or Christolube which are O2 compatible for use with nitrox. Grooves are undesirable in the seats. The deeper the groove, the more performance will be degraded. I make my own LP seats (http://www.scubaboard.com/forums/re...85694-scubapro-r190-r380-r390-nylock-nut.html) but I am also looking for an aftermarket source for those seats for the less adventuresome. I'm waiting on a delivery of aftermarket HP and LP seats that hopefully will work with MK2/5/7/10 1st stages and balanced and unbalanced SP 2nds.