Earnes did the FX Impact Master Class on YouTube. My Impact is also down, with a very slow regulator leak. I can shoot, but it's irritating when it won't hold air, so I've ordered parts from FX and will begin the adventure of rebuilding in a week or two. Family responsibilities keeping me from making progress right now, and parts won't ship till tomorrow.
If you call FX for parts, you can ask to have a tech call you back for consultation (they called back next day for me). He confirmed that my leak is the regulator, somewhere, so next project will be to put new o-rings through the entire regulator. There are several techniques to remove the Delrin regulator Post, the Master Class videos on the FX Channel cover that. AoA also has a Regulator Rebuild video with a different method to remove the regulator.
An O-Ring kit just for the regulator (if that's where the leak is) costs $10 plus shipping. The kit with the Regulator Post is $44. Get on the FX Web Site and download the Impact schematics with parts list if you haven't already done so. A full o-ring rebuild kit is $40 from FX, or if you look carefully, there's a British outfit that sells the kit out of Britain for $20 on eBay.
I ordered the o-ring kit with the regulator post, and a second 0-ring kit just for spares. with shipping was about $60 for parts, and next week, I should have some time to tear into the regulator.
Good luck, let us know how it goes.