magento customize onepage checkout process

I want to customize the onepage checkout process in magento in such a way that step 1 consists of shopping cart if user logged in otherwise login form and after login cart should be there. now in 2nd step; there should be input form of billing information, shipping information, payment methods options and shipping opti开发者_开发技巧ons. now in 3rd step, order review and 4th would be payment and last one would be Receipt and place order.

You're basically rewriting the onepage checkout at this point. The controlling JS opcheckout.js is written pretty tightly for the existing process, so don't count on being able to reuse it in any sane manner. That said, if you take a look at the actual model/block classes (Mage_Checkout_Model_Type_Onepage and Mage_Checkout_Block_Onepage, respectively) they're actually pretty cleanly written, so you should be able to steal them for your version.

http://www.excellencemagentoblog.com/magento-onestep-checkout-remove-payment-method-step You can go through above mentioned link it covers aspects of customizing one page checkout.