Interested in a prophet with a damaged key.....help!

I've come across someone selling a prophet 08 with 1 defective key. He can't tell me exactly what's wrong with it other than it doesn't register and "probably needs the contact changed



Is this something I could do? Is it an easy or difficult repair? About how much would it cost? Do you think that's likely the problem?



Worst case scenario?



Thanks so much in advance

Interested in a prophet with a damaged key.....help!