According to the front panel replacement guide, it's supposed to have the wheel in the front panel. That's most clearly visible in Step 17 (the last step): [guide|387]
The 2nd gen had a removable touch wheel, as seen in [https://www.youtube.com/watch?v=F7LkhQVuEnU&t=3m9s|this video].
I'm not finding any evidence of people separating the touch wheel from the front panel. But if it's no good to you attached to the old front panel, it might be worth trying to separate. If you do succeed in this, please document it and add a section to the above 3rd Gen Front Panel guide, so as to help others in this position.
You may also want to add it to Stories: https://www.ifixit.com/Stories. There may well be a story about this in the 148 pages there, but I'm not seeing a keyword search function for that part of the website.
Best of luck!