Check engine light came on with noticeable what I believe is fuel injector tick
on 2005 Ford Expedition

Also note slight hesitation/miss on acceleration on mild incline.

2 answers
Scan test is needed to find out why the light is on first thing! Save all the guess work.
If you believe the fuel injector is bad you can unplug one connector at a time from each injector. If there is a change in the idle or it runs worse/rough the injector you unplugged is a good injector. Plug each injector back in after checking it. If you have a bad injector the engine will not change idle when unplugged. Of coarse the engine must be on when checking these.