P0772 - Foooord Fusion 2006

Question

Wrench and engine light turned on while driving. I had trouble sfifting into first gear for the past 6 months. My friend mechanic said that it was solenoid going out. I got code the p0772 at Auto Zone. Had some research done and it said that before changing solenoid e I need transmission flush done. I am not sure I want to do that. Is this the sign my transmission is going out?