Without seeing the code I will do my best to answer. What you need to do is setup a new route and in that controller in the indexAction method you need to call the current method with any parameters.
So in Magento a URL is structured as follows:
e.g. catalog/product/view/id/1 would be Mage_Catalog_ProductController->viewAction() and $_GET['id'] = 1
So if you take your current URL it could be
- marketplace = controller
- seller = method
- profile - parameter key
- shopname = parameter value
It could also be that the controller is a sub directory calling the shopName method or the indexMethod.
So if you were to create a custom controller you create a module and do the following.
1. Register the route
In your etc/config.xml file you would add the following (change colin_core to vendor_package name)
2. Create Controller
So you need to create your IndexController under app/code/local/Vendor/Package/controllers/IndexController.php
So in the example below I am loading a product with an ID of 1. You need to replace the controller path and the code with Controller you are calling the code from and also the method with params you need to call.
//@TODO replace controller
class Colin_Core_IndexController extends Mage_Core_Controller_Front_Action
public function indexAction()
//@TODO replace code
$controller = new Mage_Catalog_ProductController(
Please note that if you don't pass in a request and a response they would both be set to null when you call the controller.