Ramblings from my notebook today...
The House-Amber comparisons began back in "Mirror, Mirror" when Amber's insecurity is revealed to be the same House (which he in turn revealed in "Son of a Coma Guy"): wanting to be right (and valued as a result). This comes up again in "Games." In that same episode, House also appeared reluctant to fire Amber. In "Don't Ever Change," House finally verbalizes this to Wilson in form of "Oh my god, you're sleeping with me." After Amber talks to House towards the end of the episode (her love and respect speech), he wore an expression that I always took as a certain understanding of or empathy for her. He ends up giving Wilson his blessing to be with her after that. In "Living the Dream," House and Amber unintentionally try to do the same thing - get Wilson to go after what he wants, not what he thinks he should want.
House and Amber are one and the same, except that Amber is healthier and more emotionally available (not saying she's perfect) - is she the House that Wilson first met many years ago? If Wilson didn't notice the similarities before, he definitely knew after "Don't Ever Change." So, Amber becoming ill (and even injuring her right thigh) relates back to his ever-present fear of losing House. And if she dies...?
More interesting, really, is what Amber means to House. If they weren't so busy fighting each other for Wilson's affection, they would have easily gotten along (whether that relationship be mentor/student, father/daughter, romantic/sexual). As I said earlier, Amber is a healthier, more emotionally available House. She is what he used to be and could become again. She takes care of Wilson and makes him happy in a way House currently can not.
House identifies with her, and I think "House's Head" makes a point of this. He's determined to remember who he saw dying on the bus because he subconsciously knew it was Amber and he knows what she means to Wilson (and Wilson to him) and to himself. His subconscious takes on the form of a woman in black, who turns out to be Amber. During the crash, he reaches out to her, and before passing out, tries to care for her.
In the next episode, the idea that he was having an affair with her is planted in House's mind. The scenes with the woman in black (subconscious) also had a sexual air, too. I highly doubt he slept with Amber (hello there, Crandall Redux!), and I don't believe the sexuality on display was literal, the physical intimacy serving as an emotional intimacy (again, relating to Amber, and what she means to Wilson). Maybe they had a conversation in those missing four hours in which they came to a mutual understanding?
The next episode, House is asked to risk his life to save Amber. He's going to do it. One, he will symbolically be trying to save himself. Two, if he can't fix himself to make Wilson happy, he's going to fix her, at least. But I'm sure she'll die anyway. And that's when this will get really interesting in setting up for Season 5 (which us spoiler whores know starts with a House/Wilson storyline).
House and Wilson's relationship is the only one that gets tested every season. Since TPTB obviously aren't interested in splitting them up, they are repeatedly demonstrating the strength and intesnity of House and Wilson's love for each other. And I'm more than happy to watch.
(Testament to this episode: My mom, a casual viewer, feels the need to rewatch this and acknowledges the symbols/themes. GO TPTB!!)