I have a friend whose father was similarly attacked. In his case, the files were not actually encrypted and my friend was able to get around the problem. As I recall, this involved booting the PC in Safe Mode and manually removing the offending virus after many tedious hours. If you don't have technical chops, I wouldn't attempt the removal on your own.

In the worst scenario, your files may actually be encrypted, which I hope is not the case. As I understand it, you actually will get access to your files if you pay the ransom, but not for long.

What interests me is that these attacks are on the rise and extortion like this would clearly seem to be a felony, but I guess most prosecuting attorneys are uninterested in complex property crimes.