Updating apps when have a new ID and password
I am trying to update apps that I first downloaded using an ID (old email address) and password I don't remember. When I tried to update them, it kept asking for my password. when I try to put my new one in, it just asks for it again. I was told at a local apple store I needed to remove the apps and then go to the ITunes store and re-buy then. When I do that, I'm told they're already downloaded. Some, like Yelp, Waze and Trip Advisor, I really want.
IMac, Mac OS X (10.4.2)