Ajax :: Change Forms In Page [from PHP]?

I've got 2 questions about ajax

1.How can I change forms in a page using ajax?I am trying to do something like that:

stage1: page.php
Enter First Value: ____________
[Send]

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after pressing send im sending the data to itself to "page.php"and then sending it to another website and waiting for a return value.

This is the stage 2 form:
stage 2: page.php
Enter Some value: __________
Enter another value: __________
[Send]

So how can I do that on ajax so the whole page wont need to reaload with the stage 2 form and only reloading "stage 2" form ?

2. How can I place some kind of picture untill I recive the return value from my first form and only after that showing the second form..?