Hi Trivium and welcome to the Ford Fusion Club. More information is needed to offer any sort of accurate information. Such as: Is your 2010 Fusion equipped with the built-in Navigation? Is it equipped with SYNC (a possible larger issue)? Does it have the Sony sound system (another possible issue) etc.etc.?
Here is some fact and some opinion. Fact...You are taking a chance with old OEM units. Same units, same age, same issues.
Fact...
You can can find aftermarket audio units for far less than $400, with far better sound and features than the 2010 system offered. Plus, you will not be taking a chance on purchasing a 12 year old unit which may/will have the same problems in short order as the one you replaced.
Just for grins, go to Crutchfield:
Crutchfield: Car Stereo and Audio, Speakers, Home Theater, Pro Audio, TVs
Use their "Find what fits your car" tool, and see what your other options are. They offer all you need to remove/install a new unit, including all the necessary wiring harnesses/connectors, face plates, detailed removal/installation instructions, lifetime tech support etc etc.
Opinion: Unless you are dead-set on keeping the dash looking "factory" and/or keeping all SYNC functionality (if applicable), you will almost certainly find better solutions to your issues. Even for the original SYNC.
Let us know how you make out and good luck.