Hello everyone,
I am new to the site and know nothing about pianos/keyboards so please forgive my horrible music language

My boyfriend borrowed the Yamaha Clavinova clp-550 from a family member to use for music producing and it stopped working after a couple of months. I know the keyboard is about 10 years old, but we are in one of those situations where it would have stopped working sooner or later but stopped working in our possession. There are about 10 white keys and five or six black keys in the middle of the keyboard that stopped working. Every key around those keys works fine. Any ideas? Cost for repairs?
Also since the piano is more that 10 years old, we were just thinking of buying it off of the family member. How much do you think one of these would sell for? I've seen from $200-500.