If the financial institution is not listed in the FIDir.txt that gets installed with your Quicken and updated with each Online Update (or One Step Update), then you won't be able to setup online services with them in Quicken.
Quicken Windows 2013 is the only Quicken product that has online services (download transactions) available for loan accounts, at the time of this posting. All other products would have been manual data entry, so it wouldn't matter if the financial institution is supported by the FIDir.txt or not.
If your loan account is in Quicken 2013 and enabled for online downloads with GMAC, and your loan was paid off at GMAC by Ocwen, GMAC will transmit payoff and closing statement information to Quicken taking that account to a zero balance and allowing you to close it in your data file. You would then setup a new, manual Loan account for Ocwen to track your principal + interest payments and link that liability to the asset you had assigned to the GMAC liability.