Recommendations HD Upgrade iMac 27 ?Fan Issues? Anyone With Experience?

I have an iMac 27 inch refurb (mid 2011) on the way - decided to upgrade since I do use the optical drive a lot for tranferring pictures among family members and burning discs for my kids' classes and the new one eliminates optical drives (and makes upgrading nearly impossible).

Anyway, the only available model had a 1 TB drive and I would like to upgrade that to 3 TB. In fact, I have a 3 TB Seagate drive which would be perfect for this. In researching the upgrade I have come across reports of issues regarding the upgrade as causing problems whereby the fan runs at full speed all the time after the install.

I am posting this question since I've seen a lot of conflicting information on whether or not the drive substitution can be made. It seems that Apple has chosen to get HD temperature information via a weird proprietary means and that use of a different drive messes the system up such that the drive reads hot and fails Apple Harware Test and causes the fan to run. One source claimed that if a white dot on the HD connector is facing "up" that there is no issue. Others indicated the need for manufacturer-specific cable (though that might be for an earlier model iMac, I was not clear on that). Still another source (OWC) indicated that the upgrade could really only be done by them professionally by sending the computer and a lot of money to them.

Anyone out there with direct experience / feedback on this?

Bob