Magento - PayU Payment Plugin

We need a plugin created from scratch 100% compatible with all the current non-beta versions of Magento.(At least 1.5.x up to 1.7.x) 1. The Plugin should be able to be installed as an extension via Magento Connect and also downloading a ZIP from an URL if a manual installation its necessary. 2. The following settings should be able to be configured from within the Administrator at [admin => System => Configuration => Payment Methods] 2.a. Title: Text that will be shown to the customer as payment gateway. 2.b. Enable: This field should allow to the user to activate or deactivate the plugin. 2.c. UsuarioId: This field should receive the userid (one will be provided for testing purposes). 2.d. Llave encripción: This field should receive the encryption key (one will be provied for testing purposes). 2.d. Prueba: This field should have this two options [yes] (test mode on) and [no] (test mode off) 2.e. Payment service URL: This field should receive the URL of the payment gateway. 3. The payment gateway we are connecting with returns to magento the order status a long with other information. 4. At the front end should work as any other payment plugin (Paypal, Money bookers, Credit Card, etc) which typically is shown automatically in the payment methods during checkout process as long as the payment method (payment plugin) is marked as active inside of the administrator. 5. The payment will redirect the user to the Service URL and after the process returns to the virtual store. 6. Details about manual integration instructions are in English and Spanish. If the manual in english attached is not available, also can be downloaded from: [login to view URL]