Metal finish work isn't hard with some power tools, just time consuming, that's about a 4. The holes in the TG are a little on the tight side, a pin wouldn't just slide in, I had to clean them up a bit with a drill bit by hand. Other than that, it fit pretty good. The spacer is on the thick side, so it will be tight, it's also rough so it can be thinned down and finished and won't need much if any shimming, screw holes are perfect.
The first trigger job is about a 7 or 8, but once you have one under your belt, they become a 3 or 4.
The anxiety of the first trigger job is the biggest hurdle, actually doing it isn't all that hard. Of course some people just aren't inclined to be the DIY type, so it's harder, plus if they aren't DIYers, they likely don't have the tools that go along with it.
Tim