PHP & XML first time user help..

Right about to walk into the deap end of PHP & XML. Not much I don't know about normal PHP programming but my XML knowlage is very limitated....I know what it is and what its for and "get it" but thats about it...... Got my "bible" out WROX Proffesional PHP4 and have started reading..... What I really want to know what Model to use! SAX or DOM? or PRAX? I am going to be interacting with a hotel/flight/car rental XML feed (Travelnow if anyone has done it before...). Doing searhes on it and placing orders hopefully etc. Where the feck do I start... Any good semi-advanced tutorials would be good also if anyone knows of any. And any recomendations on any pre build classes out there to make my life easier! Cheers John Wards SportNetwork.net