New payment module, what return page to use and how to let user choose module

[alinux]

Hi
I did follow http://virtuemart.net/documentation/Developer_Manual/Extensions.html#N20808 to setup a new payment module.
My module redirects the user to the payment gateway and the user is then sent back to virtuemart. I have two questions

1- To which page should the user be redirected, in case of virtuemart + Joomla ?
2- The code I have is a single page that starts a class and then redirects the user to the payment gateway. When I did create this payment module and I did put the two files into the payment directory and I enabled the payment module. Now when I checkout the user is directly redirected to the payment gateway instead of allowing him to choose from the list of available payment modules, is this normal ?
Thanks

[alinux]

Anyone please ?