Obviously what you need to do first is to get your car back, and under your control.
Next if the dealership will tell you what codes they got from the computer, post them here. There are a number of resources to help sort out the codes.
If the dealership won't tell you what they got for codes, if the car is driveable, go to Autozone or other major auto parts retailer and they will dump them for free. If you are a DIY'er you can dump the codes yourself. Walmart sells a $30 or so hand scanner that will do the trick. See
http://www.actron.com/product_detail.php?pid=16153 for an example of what the inexpensive hand scanners look like.
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See
http://www.troublecodes.net/Ford/
OR
See
http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See
http://www.mustangworks.com/articles/electronics/eec-iv_codes.html
IF your car is an 88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 88's except possibly the Cali Mass Air cars.
Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.