I don't mean to sound harsh here but if you are installing exchange for a customer then your knowledge needs to be much better than it is now.
Take a course or buy a few books, test exchange on a test bed and have a play with it. Installing and the initial setup of exchange are the easy bits. What are you going to do if your customer has a real problem a few months down the line? Or a server needs to be restored?
I'm all for learning new technologies and software but you need to be careful when messing with businesses.