And that's just the kind of comment from a ****** that stops people from learning about things. In case you didn't realise the whole point of a forum is one of information exchange and helping members who are not as well informed as others.
As for your level of knowledge, have you even tried to completely replace the stock dialler on any modern Android phone? If you had, you'd understand that the question is a valid one and certainly on a Streak, as far as I understood (and I'm no expert and that's why i'm asking) it can't be attempted without rooting and even then it's doubtful that it will be sucessful.
"Dude its simple... you just install the dialer you want to use and set it as the default dialer app"
Perhaps you should use Google or Yahoo before you respond 'dude'.