Audiovox CDM-8910 / PM-8912 / Flasher V7

ahhhh!!
I bought this new phone audiovox 8910) for my little sister..and they said in the faceplate instructions that I also purchased that you can do it yourself..well I did..and now the internal screen doesn't show..the phone still works..(makes calls recieves call etc)..but the display does not appear?!
i have no idea what to do? ...if this will cost more money to have it fixed or if it's something that hopefully i can try and correct myself

thank you for anyone that can help me out