Need help on old music

I have a elderly neighbor who has some very old reords, she is in dire need of money and asked my help on finding its value, I am a long time member of audiogon but I have no experience in this field, ther are many old 78 recodings most in 6 to 8 condition, she also has a boxed set of of the original south pacific by rodgers and hammerstein with the original cast, the box is in 7 condition due to age, the records and jackets are in 9 condition, can anyone shed some light on where I can get info on the value of these, thanks