Your experience was similar to mine. I've also been waiting a while for a diesel allocation and my dealer called yesterday and said it could move forward. When I asked if they got "2" diesel allocations (since there was 1 diesel order in front of me) he said he isn't currently showing the diesel on constraint. I don't know if this is a temporary thing or what, but certainly good news for those of us interested in the diesel.
Regarding the front/rear black GMC logo, I'm also going to do this. My wife likes it a lot more than red. As the post above by
@Banks22 shows, you have to buy it from the parts department/online afterwards. It isn't possible to add it at factory order time. The black nameplates in the order system are something different as a post above by
@swathdiver suggests.