Unfortunately I think you're right. According to the manual the grille, front fascia/bumper, and "impact bar" must come off. The hooks actually attach to the impact bar, which is kind of like a thick metal bumper that sits just behind the flexible plastic bumper.
So yes, it looks to be quite a job unless there is some way to sneak the hooks in from underneath or behind. I really wish my Envoy had tow hooks and even looked at the manual to see how the factory hooks are attached. I remember being sufficiently scared away to forget about going that route. Plus there are no openings in the nose and I don't want to cut any.
Other options include a D-ring that attaches to the hitch receiver or just attaching a tow line with hooks to someplace sturdy on the frame. The tow hooks would obviously be ideal though.