Clark,
Glad you finally snagged one. As for parts, the HuMa seems like on of those "upgrades" that I liken to a cold air intake on cars. Do you really think the manufacturer didn't do his homework to provide an appropriate component. If the OE goes bad, sure, why not. I have 4 Edguns with the EDMU and they all still work and I've never changed a battery. I will admit the complexity and necessity to activate it are less appealing than glancing at an analog gauge. My new L2 has an analog, so thinking has changed for Ed. A set or two of O-rings and an extra valve poppet probably would be all you need. I haven't had to replace anything yet, but my usage is low, so I'm not actively trying to wear them out at this point. The nice part, is they are so easy to work on. I personally would not recommend the trigger modification, seems like a can of worms with limited improvements. I know that there will be others that call me a heretic, but I don't find the triggers to be an issue. After years of powder burners, most all airgun triggers are better than I was ever used to. Shoot it and enjoy!
Mark