the entertainment screen went black but the radio still works what could be

The unit itself has most likely had a display failure which will require removing the stereo to fix. Stereo removal is often kind of complex and it's easy to damage trim pieces if correct removal procedures are not followed. This link is probably the best for stereo removal procedures http://www.carstereohelp.com/stracura.htm , this link has some free stereo removal procedures for some cars http://www.installdr.com/InstallYourself.asp . There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online . They have very clear stereo removal procedures. Once the stereo is out Google "automotive original equipment stereo repair", I've had lots of OE stereos repaired.