When the overdrive off light keeps blinking on your Ford, that's typically a sign that the computer has detected an issue somewhere in the transmission. The Powertrain Control Module (PCM) will need to be checked for fault codes. The codes should provide you with the information on what's wrong, so you know which direction to head in.
Cars are tough to troubleshoot! If you have the manual - sometimes you can find if/then case scenarios. Unfortunately MML doesn't have any auto manuals (I double checked) but they do have a category specific page for vehicles (see link below). On the page there is a service scheduler to assist you with setting up a service. I've noticed a lot of service special offers - so perhaps you can get a deal.
I once brought my car into a shop because my "check engine" light was on and the mechanic told me a quick rule of thumb:
A) If the light is orange/yellow - no rush - but you should think about scheduling an apt to bring your vehicle into the shop.
B) If the light is red - you should bring your vehicle in immediately.