I understand that you have a couple of questions regarding the Slingbox PRO-HD.
First question - Is this the right version to get?
Short answer is yes. You can select among the Slingbox PRO-HD and the Slingbox SOLO, since these are the only models that will work in a proper way with the SlingPlayer for iPad and SlingPlayer for Android Mobile devices.
Second Question - I have plugged in the new Sling Box Pro-HD using the same leads as my old Sling Box but when I try and configure my new Pro-HD the page says it's loading but nothing happens. Is there a solution?
As the first step, I recommend you to reset the Slingbox PRO-HD. The following link will provide you with the steps to follow in order to know how to reset your Slingbox PRO-HD:
Then, you will be able to run now the Setup Assistant for Internet Viewing. If the error message persists, I encourage you to check if your computer Operating System and web-browser versions are supported or not:
Hope this helps!