This is a (belated) follow-up to your response but it may help others. First, to get the OEM assy out, I had to grind the head of the spinning bolt off. I used a Vermont American grinding point chucked into an electric drill motor. It took about 45 min. The rest is rather simple. Remembering to mark the position of the hood latch so that it can be repositioned precisely is important, too.
Upon receiving a replacement headlight assy, I checked the threaded inserts just to be certain they were properly secured. And sure enough, one spun easily. I had even used anti-seize lube on the threads of the OEM bolt used to test the inserts. While waiting for another replacement assy, I went ahead and replaced the cracked lens on the OEM unit with a lens that I had previously procured. Easy swap. One just pops off 8 metal clips, fits the new lens and foam rubber gasket, and re-installs the clips. The reflector coating on the inside of the assy still looked good (but I did not attempt to clean it). If your V70 has headlight wipers, remember to swap the wiper stop on the base of the headlight assy. It's just one screw. When re-installing the assy, I concur with your recommendation to be careful to install the 3 bolts. If there's a spinning insert, hand tight is about all that can be used safely.
Probably the one thing that I didn't expect was when removing the side/turn signal assys that are adjacent to the headlight assys. To disengage them, one presses down on a plastic tong of the assy. Be careful not to press too hard as the plastic material can be brittle and crack easily.

Aside from the unexpected issues that pop up, the R&R process is straightforward. Thanks for your help.