You bet! Any time. That's what we're here for. And hey, we're all volunteers and just other SG members...we want this place to operate well and for the community to be the awesome thing we know it can be. :)

No worries! Believe me, this has happened to all of us. It's just part of learning the ropes around here. :)

Yes, this has been brought up before, but I'll add it to the very long list of suggestions for CG. :)

One thing you can do is to have ESGST help you out with this. If you're not already running ESGST, download and install that plugin first (you can easily find the detail thread about it in the discussions section). And then you can turn on all sorts of different tagging, including not only DLC, but whether or not you own the base game as well as whether you own the DLC. I color-code mine as well so that they show up very differently (owning the base game is purple, and the owned tag for the DLC is teal). If I see the teal tag on something, the very next thing I do is hide that DLC so it won't show up in lists any more.

Same goes for packages where I own 100%. I hide them all as I go. :)