You should be able to exchange money at the airport but that will be the worst exchange rate.
ATMs are becoming universal. I know I used them in Vn. Think I used them in Cam? You might be able to get cash advances/exchanges at banks on your CC, though of course you will be hit with fees.
Side note: When you go to Peru (Machu Picchu lives up to the hype and Kuelap is worth the visit) they love Visa, Mastercard not as much. I got a little jammed, even at international banks. South America = Visa.
Travel books can be a bit dated in places that are quickly changing like Cam and Vn, as I found out on my trip. Again we found Wikitravel and Lonely Planet sites useful.
http://wikitravel.org/en/Main_Page
Again as Travisimo mentioned you can do pretty easily find housing and transport when you are there. Though that may vary a bit if it is peak season. We travel right when the world economy crashed and it was off season. There still were tourist but thinner than usual.
-Peter
Sounds like you have housing all set but will say be careful of locals that meet you at the bus/airport offering their place. They might be safe but you are definitely not getting the best price. We had a owner follow us from the bus and we are pretty sure he was telling all the other Guest house owners (in Vietnamese) to tell use that they were full. So while one of use checked out his place (it looked fine) another friend slipped away and checked out other places. Guess what, we found tons of places that were available.