Yeah I think it was a recent addition. That being said, every mechanic I've talked to in the last couple of years had some pretty unpleasant things to say about Dorman replacement parts. I too had a good result with the 3800 upper intake manifold plenum, as I had two of those engines that required that fix. However, it's been many years since they released that part. Quality seems to have dropped since then.
It might be intimidating, but I can assure you it's fairly straightforward. It would just suck to spend $165 on a Dorman manifold only to have it sit around afterward. I've shipped over 200 of these kits and received feedback via e-mail and on this forum, and everyone has noted it was a pain-free repair process.
The drilling is surprisingly quick, and the gluing is more of a caulking. Its purpose is to plug up the hole and keep the screw from backing out. To be totally honest, if you do that part first, it will be dry enough by the time you have the intake manifold back in the car to start it up and drive around. It's also a cheaper fix by $30 and is serviceable. I'll actually update that thread shortly here to offer replacement check valves in case anyone wants to replace theirs for any reason. I can ship a check valve out for $15.
I'm just not a fan of PCV systems that aren't serviceable and prone to leaks. From what I'm seeing in the pictures, the Dorman manifold does not have a serviceable PCV system, so once it gunks up with some PCV crap, it will either leak or suffer the same fate as the GM manifold, both of which are design flaws inherent to this manifold.