Your model should be quite salvageable. What ever you do DON'T USE SANDPAPER! There are a number of products that will remove most paints from styrene plastic safely. Some of the products which are specifically made for this purpose is a product called Scale Coat, and another is made by Floquil and is called "Easy Lift Off" or ELO.

Both products work very well. However, some industrial products such as brake fluid, Wesley's Bleech-White. Mr. Clean and simple green have been used. Once your model has been stripped, wash and dry it thoroughly, re-prime, and you should be good to go!